I created a script that searched through the files of SMF (2 for right now) that grabs all of the keys from variables. It only works for $var['{KEY}']. I should come up with a better way to document it.

allow_disableAnnounce

1. Post.php
2. Profile.template.php

allow_editDisplayName

1. Profile.php
2. Register.php

allow_guestAccess

1. LogInOut.php
2. index.php

allow_hideOnline

1. Profile.php

allow_hide_email

1. Display.php
2. Groups.php
3. Load.php
4. Memberlist.php
5. News.php
6. PersonalMessage.php
7. Profile.php
8. Register.php
9. Search.php
10. Subs-Auth.php
11. Subs-Members.php

allow_ignore_boards

1. Load.php
2. Profile.php

allow_sm_stats

1. Stats.php

approveAccountDeletion

1. Profile.php

attachmentCheckExtensions

1. Post.php
2. Subs-Post.php
3. Post.template.php

attachmentDirSizeLimit

1. ManageAttachments.php
2. Post.php
3. Subs-Post.php

attachmentEnable

1. Display.php
2. Post.php

attachmentEncryptFilenames

1. Subs-Post.php
2. Subs.php

attachmentExtensions

1. Post.php
2. Subs-Post.php

attachmentNumPerPostLimit

1. Post.php
2. Post.template.php

attachmentPostLimit

1. Post.php

attachmentShowImages

1. Display.php

attachmentSizeLimit

1. Post.php
2. Subs-Post.php
3. Post.template.php

attachmentThumbHeight

1. Display.php
2. Subs-Post.php

attachmentThumbWidth

1. Display.php
2. Subs-Post.php

attachmentThumbnails

1. Display.php
2. Subs-Post.php

attachmentUploadDir

1. Display.php
2. ManageAttachments.php
3. Post.php
4. Profile.php
5. Subs-Graphics.php
6. Subs-Package.php
7. Subs-Post.php
8. Subs.php

autoFixDatabase

1. Database.php
2. Subs-Db-mysql.php
3. Subs-Db-postgresql.php
4. Subs-Db-sqlite.php

autoLinkUrls

1. Subs.php

autoOptMaxOnline

1. ScheduledTasks.php

avatar_action_too_large

1. Load.php
2. Profile.php
3. Subs.php

avatar_directory

1. ManageAttachments.php
2. Profile.php
3. Subs-Package.php

avatar_download_external

1. Profile.php

===avatar_download_png

1. Subs-Graphics.php

avatar_max_height_external

1. Load.php
2. Profile.php
3. Subs.php
4. Profile.template.php

avatar_max_height_upload

1. Profile.php

avatar_max_width_external

1. Load.php
2. Profile.php
3. Subs.php
4. Profile.template.php

avatar_max_width_upload

1. Profile.php

avatar_resize_upload

1. Profile.php

avatar_url

1. Load.php
2. Profile.php
3. Subs.php
4. Profile.template.php

banLastUpdated

1. Security.php

bbc_disabled_disabledBBC

1. ManagePosts.php

bbc_disabled_signature_bbc

1. ModSettings.php

cache_enable

1. Database.php
2. Load.php
3. MoveTopic.php
4. News.php
5. Search.php
6. Subs-Auth.php
7. Subs-Db-mysql.php
8. Subs-Db-postgresql.php
9. Subs-Db-sqlite.php
10. Subs.php

cache_memcached

1. Load.php

cal_allow_unlinked

1. Calendar.php

cal_allowspan

1. Calendar.php
2. Post.php
3. Subs-Calendar.php
4. Post.template.php
5. Calendar.template.php

cal_days_for_index

1. SSI.php
2. BoardIndex.php

cal_daysaslink

1. Calendar.template.php

cal_defaultboard

1. Calendar.php
2. Post.php

cal_enabled

1. BoardIndex.php
2. Calendar.php
3. Display.php
4. ManageCalendar.php
5. Subs.php

cal_maxspan

1. Calendar.php
2. Post.php
3. Subs-Calendar.php
4. Post.template.php
5. Calendar.template.php

cal_maxyear

1. Calendar.php
2. Post.php
3. Subs-Calendar.php
4. Post.template.php
5. Calendar.template.php
6. ManageCalendar.template.php

cal_minyear

1. Calendar.php
2. Post.php
3. Subs-Calendar.php
4. Post.template.php
5. Calendar.template.php
6. ManageCalendar.template.php

cal_showInTopic

1. Display.php

cal_showbdays

1. BoardIndex.php
2. Calendar.php

cal_showevents

1. BoardIndex.php
2. Calendar.php

cal_showholidays

1. BoardIndex.php
2. Calendar.php

===cal_showweeknum

1. Calendar.php

censorIgnoreCase

1. Load.php
2. Admin.template.php

censorWholeWord

1. Load.php
2. Admin.template.php

censor_proper

1. Load.php
2. ManagePosts.php

censor_vulgar

1. Load.php
2. ManagePosts.php

compactTopicPagesContiguous

1. Subs.php

compactTopicPagesEnable

1. Display.php
2. Subs.php

cookieTime

1. LogInOut.php
2. ManageServer.php
3. Profile.php
4. Register.php
5. BoardIndex.template.php
6. Login.template.php

coppaAge

1. Register.php
2. Register.template.php

coppaFax

1. Register.php
2. Register.template.php

coppaPhone

1. Register.php
2. Register.template.php

coppaPost

1. ManageRegistration.php
2. Register.php

coppaType

1. Register.php
2. Register.template.php

copy_settings

1. Admin.php

copyright_key

1. Admin.php
2. Subs.php

countChildPosts

1. BoardIndex.php
2. MessageIndex.php

custom_avatar_dir

1. ManageAttachments.php
2. Profile.php
3. Subs-Graphics.php
4. Subs-Package.php

custom_avatar_enabled

1. ManageAttachments.php
2. Profile.php
3. Subs-Graphics.php

custom_avatar_url

1. Load.php
2. Profile.php
3. Subs.php

databaseSession_enable

1. Load.php

databaseSession_lifetime

1. Load.php

databaseSession_loose

1. Load.php

defaultMaxMembers

1. Groups.php
2. Load.php
3. ManageMembers.php
4. Memberlist.php
5. Who.php

defaultMaxMessages

1. Display.php
2. Load.php
3. ManageAttachments.php
4. ManageBans.php
5. ManageErrors.php
6. MessageIndex.php
7. ModerationCenter.php
8. PersonalMessage.php
9. Profile.php
10. Recent.php
11. SplitTopics.php
12. index.php

defaultMaxTopics

1. Load.php
2. MessageIndex.php
3. Recent.php
4. SplitTopics.php
5. index.php

default_personal_text

1. Subs-Members.php

default_timezone

1. Load.php
2. install.php

deleted

1. Boardnation.php

disableCheckUA

1. Load.php
2. Security.php

disableEntityCheck

1. Load.php

disableHashTime

1. Subs.php

disableHostnameLookup

1. ManageBans.php
2. Profile.php
3. Security.php
4. ManageBans.template.php

disableQueryCheck

1. Database.php
2. Subs-Db-mysql.php
3. Subs-Db-postgresql.php
4. install.php

disableRegisterCheck

1. Subs-Members.php

disableTemplateEval

1. Load.php

disable_log_report

1. SendTopic.php

disable_smf_js

1. Admin.template.php
2. ManageSmileys.template.php
3. Packages.template.php
4. Themes.template.php

disable_wysiwyg

1. Subs-Post.php
2. Post.template.php
3. Profile.template.php

disabledBBC

1. ManagePosts.php
2. Subs-Post.php
3. Subs.php

disabled_profile_fields

1. Display.php
2. Memberlist.php
3. ModSettings.php
4. Profile.php

disallow_sendBody

1. Post.php
2. Subs-Post.php
3. Profile.template.php

displayFields

1. Display.template.php

edit_disable_time

1. Display.php
2. Post.php
3. Profile.php
4. Recent.php
5. RemoveTopic.php

edit_wait_time

1. Post.php

email

1. Constants.php
2. Boardnation.php

enableAllMessages

1. Display.php
2. MessageIndex.php
3. Recent.php

enableBBC

1. Subs-Post.php
2. Subs.php

enableCompressedOutput

1. SSI.php
2. Admin.php
3. Display.php
4. DumpDatabase.php
5. Load.php
6. News.php
7. index.php

enableEmbeddedFlash

1. Subs.php

enableErrorLogging

1. Errors.php
2. changelog.txt

enableParticipation

1. MessageIndex.php
2. Recent.php
3. Search.php
4. MessageIndex.template.php
5. Recent.template.php

===enablePostHTML

1. Subs.php

enablePreviousNext

1. Display.php

enableReportPM

1. PersonalMessage.php
2. PersonalMessage.template.php

enableSpellChecking

1. Display.php
2. PersonalMessage.php
3. Post.php
4. Profile.php
5. Search.php

enableStickyTopics

1. Display.php
2. LockTopic.php
3. MessageIndex.php
4. Post.php
5. Recent.php
6. Search.php
7. SplitTopics.php
8. MessageIndex.template.php
9. Recent.template.php
10. Admin.template.php

enableVBStyleLogin

1. BoardIndex.php
2. Subs.php

enable_buddylist

1. Load.php
2. Profile.php
3. Subs-Post.php
4. PersonalMessage.template.php

failed_login_threshold

1. LogInOut.php

fixLongWords

1. Subs.php

forum_alias_urls

1. Load.php
2. Subs-Auth.php

globalCookies

1. Load.php
2. Security.php
3. Subs-Auth.php

global_character_set

1. Load.php
2. ManageMaintenance.php
3. ScheduledTasks.php
4. Subs.php

guest_hideContacts

1. Display.php
2. Load.php
3. Memberlist.php
4. News.php

guest_post_no_email

1. Post.php
2. Post.template.php
3. Wireless.template.php

hitStats

1. Stats.template.php
2. Xml.template.php
3. index.php

host_to_dis

1. Subs.php

hotTopicPosts

1. Display.php
2. MessageIndex.php
3. Recent.php
4. Search.php
5. MessageIndex.template.php
6. Recent.template.php

hotTopicVeryPosts

1. Display.php
2. MessageIndex.php
3. Recent.php
4. Search.php
5. MessageIndex.template.php
6. Recent.template.php

integrate_activate

1. ManageMembers.php
2. Profile.php
3. Register.php

integrate_buffer

1. Subs.php

===integrate_change_member_data

1. Subs.php

integrate_delete_member

1. Subs-Members.php

===integrate_egg_nog

1. ViewQuery.php

integrate_exit

1. Subs.php

integrate_fix_url

1. News.php

integrate_login

1. LogInOut.php

integrate_logout

1. LogInOut.php

integrate_magic_quotes

1. QueryString.php

integrate_outgoing_email

1. Subs-Post.php

integrate_personal_message

1. Subs-Post.php

integrate_pre_include

1. Load.php

integrate_pre_load

1. Load.php

integrate_redirect

1. Subs.php

integrate_register

1. Subs-Members.php

integrate_reset_pass

1. Profile.php
2. Reminder.php
3. Subs-Auth.php

integrate_validate_login

1. LogInOut.php

integrate_verify_password

1. Profile.php
2. Security.php

integrate_verify_user

1. Load.php

integrate_whos_online

1. Who.php

karmaApplaudLabel

1. Display.template.php
2. PersonalMessage.template.php
3. Profile.template.php

karmaLabel

1. Display.template.php
2. PersonalMessage.template.php
3. Profile.template.php

karmaMinPosts

1. Karma.php
2. Load.php

karmaMode

1. Karma.php
2. Load.php
3. News.php
4. Profile.php
5. Display.template.php
6. PersonalMessage.template.php
7. Profile.template.php

karmaSmiteLabel

1. Display.template.php
2. PersonalMessage.template.php
3. Profile.template.php

karmaTimeRestrictAdmins

1. Karma.php

karmaWaitTime

1. Karma.php

knownThemes

1. Load.php
2. Packages.php
3. Profile.php
4. Themes.php

language

1. Boardnation.php

lastActive

1. Subs.php
2. BoardIndex.template.php

last_mod_report_action

1. Security.php

latestMember

1. Boardnation.php
2. ManageNews.php
3. Post.php
4. Profile.php
5. Subs.php

latestRealName

1. Boardnation.php
2. ManageNews.php
3. Subs.php

load_average

1. Load.php
2. ScheduledTasks.php

loadavg_allunread

1. Recent.php

loadavg_auto_opt

1. ScheduledTasks.php

loadavg_enable

1. Load.php

===loadavg_forum

1. Load.php

loadavg_search

1. PersonalMessage.php
2. Search.php

loadavg_show_posts

1. Profile.php

loadavg_unreadreplies

1. Recent.php

localCookies

1. Security.php
2. Subs-Auth.php

===mail_from

1. Subs-Post.php

mail_limit

1. ScheduledTasks.php
2. Subs-Post.php

mail_next_send

1. Load.php
2. ScheduledTasks.php

mail_no_message_id

1. Subs-Post.php

mail_quantity

1. ScheduledTasks.php

mail_queue

1. ManageNews.php
2. Post.php
3. Subs-Post.php

mail_recent

1. ScheduledTasks.php
2. Subs-Post.php

mail_strip_carriage

1. ScheduledTasks.php
2. Subs-Post.php

mail_type

1. ScheduledTasks.php
2. Subs-Post.php

maxMsgID

1. SSI.php
2. Display.php
3. Load.php
4. ManageMaintenance.php
5. MessageIndex.php
6. MoveTopic.php
7. News.php
8. Recent.php
9. RemoveTopic.php
10. Search.php
11. SplitTopics.php
12. Subs-BoardIndex.php
13. Subs-Boards.php
14. Subs-Post.php
15. Subs-Recent.php

max_image_height

1. Display.php
2. Subs-Post.php
3. Subs.php

max_image_width

1. Display.php
2. Subs-Post.php
3. Subs.php

max_messageLength

1. ManagePosts.php
2. PersonalMessage.php
3. Post.php

max_pm_recipients

1. ModSettings.php
2. PersonalMessage.php

memberCount

1. Load.php
2. changelog.txt===

memberlist_cache

1. Memberlist.php

memberlist_updated

1. Memberlist.php

messageIconChecks_disable

1. SSI.php
2. Display.php
3. MessageIndex.php
4. Recent.php
5. Search.php

messageIcons_enable

1. ManageSmileys.php
2. Subs-Editor.php

modlog_enabled

1. Subs.php

mostDate

1. Stats.php
2. BoardIndex.template.php

mostOnline

1. Stats.php
2. Subs-MembersOnline.php
3. BoardIndex.template.php

mostOnlineToday

1. Subs-MembersOnline.php
2. BoardIndex.template.php

mostOnlineUpdated

1. Subs-MembersOnline.php

new_avatar_data

1. Profile.php
2. Subs-Graphics.php

news

1. ManageNews.php
2. Subs.php

next_task_time

1. Load.php
2. ScheduledTasks.php

notify_new_registration

1. Subs-Post.php
2. Register.template.php

number_format

1. Load.php

oldTopicDays

1. Post.php

onlineEnable

1. Display.template.php
2. PersonalMessage.template.php

package_disable_cache

1. Subs-Package.php

package_make_backups

1. Packages.php
2. Subs-Package.php

package_path

1. Subs-Package.php

package_port

1. PackageGet.php
2. Packages.php
3. Subs-Package.php

package_server

1. PackageGet.php
2. Packages.php
3. Subs-Package.php

package_username

1. PackageGet.php
2. Packages.php
3. Subs-Package.php

password_strength

1. Subs-Auth.php
2. Register.template.php
3. Reminder.template.php
4. Errors.english.php

permission_enable_deny

1. Load.php
2. ManagePermissions.php
3. Reports.php
4. ManagePermissions.template.php

permission_enable_postgroups

1. ManageMembergroups.php
2. ManageNews.php
3. ManagePermissions.php
4. Reports.php
5. ManageMembergroups.template.php

pm_posts_per_hour

1. ModSettings.php
2. PersonalMessage.php

pm_posts_verification

1. ModSettings.php
2. PersonalMessage.php

pm_spam_settings

1. ModSettings.php
2. PersonalMessage.php

pollMode

1. Display.php
2. MessageIndex.php
3. Post.php
4. Recent.php
5. Search.php
6. MessageIndex.template.php
7. Recent.template.php

posts_require_captcha

1. Post.php

queryless_urls

1. News.php
2. QueryString.php
3. Subs.php

recycle_board

1. SSI.php
2. News.php
3. Profile.php
4. Recent.php
5. RemoveTopic.php
6. Search.php
7. Stats.php
8. Subs-BoardIndex.php
9. Subs-Recent.php
10. Subs.php
11. ManageBoards.template.php

recycle_enable

1. SSI.php
2. News.php
3. Profile.php
4. Recent.php
5. RemoveTopic.php
6. Search.php
7. Stats.php
8. Subs-BoardIndex.php
9. Subs-Recent.php
10. Subs.php
11. ManageBoards.template.php

registration_fields

1. ModSettings.php
2. Register.php

registration_method

1. ManageMembers.php
2. Register.php
3. Subs.php
4. Register.template.php

removeNestedQuotes

1. PersonalMessage.php
2. Post.php

requireAgreement

1. ManageRegistration.php
2. Register.php

reserveCase

1. ManageRegistration.php
2. Subs-Members.php

reserveName

1. ManageRegistration.php
2. Subs-Members.php

reserveNames

1. ManageRegistration.php
2. Subs-Members.php

reserveUser

1. ManageRegistration.php
2. Subs-Members.php

reserveWord

1. ManageRegistration.php
2. Subs-Members.php

search_banned_words

1. Search.php

===search_custom_index_config

1. ManageSearch.php
2. RemoveTopic.php
3. Search.php
4. Subs-Post.php

search_custom_index_resume

1. ManageSearch.php

search_force_index

1. Search.php
2. ManageSearch.template.php

search_index

1. ManageSearch.php
2. Search.php
3. ManageSearch.template.php

search_match_words

1. Search.php
2. ManageSearch.template.php

search_max_cached_results

1. changelog.txt===

search_max_results

1. Search.php

search_method

1. Search.php

search_pointer

1. Search.php

search_results_per_page

1. PersonalMessage.php
2. Search.php

search_simple_fulltext

1. Search.php
2. Search.template.php

search_stopwords

1. ManageSearch.php
2. Search.php
3. Subs-Post.php

search_weight_age

1. ManageSearch.template.php

search_weight_first_message

1. ManageSearch.template.php

search_weight_frequency

1. ManageSearch.template.php

search_weight_length

1. ManageSearch.template.php

search_weight_sticky

1. ManageSearch.template.php

search_weight_subject

1. ManageSearch.template.php

securityDisable

1. Security.php

send_welcomeEmail

1. Register.php
2. Register.template.php

settings_updated

1. Load.php
2. Security.php

show_group_membership

1. ManageMembergroups.php
2. Profile.php

showsidebarAdmin

1. Admin.php
2. ModerationCenter.php

signature_settings

1. Display.php
2. ModSettings.php
3. PersonalMessage.php
4. Profile.php

simpleSearch

1. PersonalMessage.php
2. Search.php

smfVersion

1. Database.php
2. Stats.php
3. Subs-Db-mysql.php
4. Subs-Db-postgresql.php
5. Subs-Db-sqlite.php

smiley_enable

1. ManageSmileys.php
2. Subs-Editor.php
3. Subs-Post.php
4. Subs.php
5. ManageSmileys.template.php

smiley_sets_default

1. Load.php
2. ManageSmileys.php
3. ManageSmileys.template.php
4. Profile.template.php

smiley_sets_enable

1. Load.php
2. Profile.php

smiley_sets_known

1. Load.php
2. ManageSmileys.php
3. Themes.php

smiley_sets_names

1. ManageSmileys.php
2. Themes.php

smileys_dir

1. ManageSmileys.php
2. Subs-Package.php

smileys_url

1. Load.php
2. ManageSmileys.php
3. Subs-Editor.php
4. Subs-Post.php
5. Subs.php
6. Help.template.php
7. ManageSmileys.template.php
8. Profile.template.php

smtp_host

1. ScheduledTasks.php
2. Subs-Post.php

smtp_password

1. Subs-Post.php

smtp_port

1. Subs-Post.php

smtp_username

1. Subs-Post.php

spamWaitTime

1. Subs.php

theme_allow

1. Load.php
2. Profile.php
3. Themes.php
4. Themes.template.php

theme_guests

1. Load.php
2. Themes.php
3. Themes.template.php

timeLoadPageEnable

1. Subs.php

time_format

1. Load.php
2. ManageNews.php
3. ScheduledTasks.php

time_offset

1. SSI.php
2. BoardIndex.php
3. Profile.php
4. Subs.php

titlesEnable

1. Load.php
2. Profile.php
3. Profile.template.php

todayMod

1. Subs.php

topbottomEnable

1. Display.template.php
2. MessageIndex.template.php

topicSummaryPosts

1. Post.php

totalMembers

1. SSI.php
2. Load.php
3. Memberlist.php
4. Stats.php
5. Subs-Members.php
6. Subs.php

totalMessages

1. SSI.php
2. ManageSearch.php
3. News.php
4. Profile.php
5. Recent.php
6. Stats.php
7. Subs.php

totalTopics

1. SSI.php
2. Profile.php
3. Stats.php
4. Subs.php

trackStats

1. BoardIndex.php
2. Subs.php

unapprovedMembers

1. LogInOut.php
2. ManageMembers.php
3. Profile.php
4. Subs.php

userLanguage

1. Load.php
2. ManageMembers.php
3. PersonalMessage.php
4. Post.php
5. Profile.php
6. Register.php
7. SendTopic.php
8. Subs-Post.php
9. Profile.template.php

user_limit

1. ModSettings.php
2. Profile.php

visual_verification_type

1. ManageRegistration.php
2. Register.php
3. Subs-Graphics.php
4. Register.template.php

warn_enabled

1. ModerationCenter.php

warning_enable

1. ModSettings.php
2. Profile.php

warning_moderate

1. Profile.php
2. Security.php
3. Profile.template.php

warning_mute

1. Profile.php
2. Security.php
3. Profile.template.php

warning_settings

1. ModSettings.php
2. ModerationCenter.php
3. Profile.php

warning_watch

1. ModSettings.php
2. ModerationCenter.php
3. Profile.php
4. Profile.template.php

who_enabled

1. BoardIndex.php
2. Profile.php
3. Subs.php
4. Who.php

xmlnews_enable

1. News.php
2. index.template.php

xmlnews_maxlen

1. News.php