Change Details

Special:Watchlist is able to list "Pages that have been changed since you last visited them are shown in bold." I want to alert users on their user profile for that number: "X new items on your watchlist." With "wlexcludeuser = wgUsername" I can nail the items down to a few but this number would unlocially change over the days (new item com ein, old ones fallout). query.watchlist has no filter for that: https://www.mediawiki.org/wiki/Special:ApiSandbox#action=query&list=watchlist&format=json