Many veteran Wikipedians have watchlists that span thousands of articles, completely beyond the ability to effectively manage. If said Wikipedian can't edit for a certain period (say, a week), just going over the changes in the watchlist can take hours and become a chore that editors simply avoid, at the possible expense of missing vandalism and/or edits that they need to see.
There are external tools for creating and organizing watchlists in different ways, but I'd like to see many of those features built-in as part of MediaWiki. One important addition should be a tag for 'high-priority' articles, similar to how GMail has a tag for 'important' e-mail. While having multiple watchlists would support such functionality indirectly, it would be great to be able to see articles marked as 'important' inside the existing watchlist, and be able to filter them like one can now hide/show own edits, hide/show bot edits, etc.
—Ynhockey (talk) 20:49, 7 November 2015 (UTC)
This card tracks a proposal from the 2015 Community Wishlist Survey: https://meta.wikimedia.org/wiki/2015_Community_Wishlist_Survey
This proposal received 33 support votes, and was ranked #30 out of 107 proposals. https://meta.wikimedia.org/wiki/2015_Community_Wishlist_Survey/Watchlists#Watchlist_priority_options