Manual:$wgAllowCategorizedRecentChanges

Recent changes, new pages, watchlist and history: $wgAllowCategorizedRecentChanges
Allow to filter the recentchanges by a category or one of its sub(subsubsub...)categories
Introduced in version:1.6.0 (r12546)
Removed in version:1.31.0 (Gerrit change 343426; git #9acd5508)
Allowed values:(boolean)
Default value:false

Details edit

Enable filtering of categories in Recent changes.

The categorization of edited pages is only tracked after this setting is set to true. It won't work right after switching.