Original task description
It would be most useful to have multiple watchlists for a given user - a large list of personal favourites, smaller lists of a given subject, trouble spots, etc.

This functionality can be simulated by having multiple usernames, but it's not quick and easy to change usernames so as only to edit with the main username.

• Merged task description from T160981 (which takes a different angle)

I would like to be able to bookmark articles and save them to lists based on their categories, e.g. Politics, Science, Pop Culture, etc.

From what I can tell, if you want to bookmark or watch an article, you can only put them all on the same global watchlist. It'd be really useful if users could simply have multiple watchlists and adjust preferences for them accordingly, both for editing/monitoring changes, and also just for bookmarking to easily find/share favorite articles.
Merged task description from duplicate T7875: Group similar pages in watchlist (aka multiple watchlists) (see comments, too)
This is a detailed proposal of how to implement something I call "watchlist categories" (should maybe come up with better name so it isn't confused with normal categories). The idea is to make the MediaWiki watchlist more flexible and allow users to have more than one watchlist:

• By default, users only have one watchlist category called "General".
• A new page is available at Special:Watchlist/categories where users can add, rename and remove watchlist categories.
• When adding an article to your watchlist and you only have one watchlist category defined (default), the watched article will automatically be assigned to that one category (to the user, the watch proccess will look just like it does today).
• When adding an article to your watchlist and you have defined more than one category, you'll go through an additional step. This step is a simple page of checkboxes that allows you to choose which of your watchlist categories you want the article to be assigned to (if none is chosen, the article is not watched).
• The current watchlist edit page (Special:Watchlist/edit) gets an additional feature: Next to each article is a "Categories" link, that sends the user back to the pick-categories page with the checkboxes (see above).
• At Special:Watchlist, besides the Namespace popup, another popup is added called "Categories" that allows you to choose which of your watchlist categories you wish to view (maybe that HTML form should be changed into GET-style so that users can bookmark specific category views). The easiest implementation is to only allow users to view one category at a time.

Merged task description from duplicate T120777: Watchlist priority options
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:
This proposal received 33 support votes, and was ranked #30 out of 107 proposals. Discussion and votes

This task was also proposed in the Community Wishlist Survey 2016. This proposal received 47 support votes and was ranked #23 out of 265 proposals. View full proposal with discussion and votes here.

See also:

• T1352: RFC: Support for user-specific page lists
  • A discussion in the related E138: Expiring watch list entries (RFC Meeting, 2016-02-03) proposed a per-item tagging system, in order to increase the flexibility of the existing single watchlist
• T22444: Watchlist "Grouping" - essentially a duplicate of this and of T3710, but an old patch is attached
• Crosswatch, a tool resulting from T92955: An enhanced cross-wiki watchlist as an OAuth tool
• https://www.mediawiki.org/wiki/Watchlist_wishlist (partially derived from T35888: Requesting a user-centred rethink of how watchlists work)
• T5525: Cross-wiki watchlists
• T182297: Provide user-curated tags on watchlist to ease user triage