The class SpecialEditWatchlist is extended in extension, but the class is not part of the stable policy and that does not allow to extend it.
I am not sure what the best way is for the extension
https://codesearch.wmcloud.org/search/?q=extends%5Cs%2BSpecialEditWatchlist%5Cb&i=nope&files=&repos=
TODO
- https://gerrit.wikimedia.org/r/c/mediawiki/skins/MinervaNeue/+/1013600
- https://gerrit.wikimedia.org/r/c/mediawiki/extensions/MobileFrontend/+/1013603
- Make sure beta cluster visually matches production watchlist with AMC disabled
- Switch configuration for pilot wikis to use desktop HTML
- Switchover to HTML for everyone
- Respond to community feedback.
- Drop watchlist code and resolve all open technical work for this special page.