Starting point:
You have 500 pages in [[Category:Foo]]. You decide that all of them ought to be in [[Category:Bar]] instead. [[Category:Foo]] should go away.
Current process:
- Move the category.
- Edit the first page that was listed in [[Category:Foo]], scroll to the end, and replace "[[Category:Foo]]" with "[[Category:Bar]]".
- Edit the next page that was listed in [[Category:Foo]], scroll to the end, and replace "[[Category:Foo]]" with "[[Category:Bar]]".
- Edit the next page that was listed in [[Category:Foo]], scroll to the end, and replace "[[Category:Foo]]" with "[[Category:Bar]]".
- Repeat 497 more times.
There is no way to move the categories without editing each and every one of those 500 pages individually and manually replacing [[Category:Bar]] with [[Category:Foo]].
Proposed process:
- Go to [[Special:MoveExistingCategory]] and tell it the new name for the category.
- Magic happens while you wait.
- You're done.
The model in mind is Special:MassMessage, where repetitive editing tasks happen in a queue with no need for manual action (and therefore possible manual errors) by the user.
The original idea is described here: https://en.wikipedia.org/w/index.php?oldid=636466561#Mass_message_like_extension_to_help_renaming_or_deleting_categories