(Terminology: the extension is deployed on a single wiki, for the WMF case this is meta wiki, that will be referred to as the "central wiki" - this is the site where the global watchlist is accessed, but it can include changes from other, non-central wikis)

Extracted from @Alsee's description at T5525#6888987

In T5525#6888987, @Alsee wrote:

Not done. While I am impressed with userscript-hacks trying to work around missing functionality, it is still trying to work around our lack of a global watchlist. I am unclear on whether the current project can/will be developed into a global watchlist, or whether we need to reclaim the "globalwatchlist" name/urls for an actual global watchlist project? I'm not a fan of userstories but I'll try to put it in that form:

1. A new user creates an account and begins editing.
2. The user discovers a "page watch" feature exists.
3. The user begins watching various pages, possibly on multiple wikis.
4. The user clicks to view the watchlist.
5. Results are shown for all watched pages, possibly on multiple wikis.
6. The user eventually discovers preferences. They find all (or substantially-all) of the current watch options are available and functional.

• Note: The user does not know Meta exists. They should not need to learn about or go to Meta.
• Note: Steps 1 through 5 were default behavior, the new user had no need to learn about preferences yet.
• Note: The user should not have to list what Wikis they want to watch - the obvious default answer is "all wikis with watched pages". If an internal list of watched-wikis is necessary then the software can automatically log a wiki as watched whenever a page is added, and log it as unwatched when the last watch on that wiki is removed. Example Use Case: Malicious individuals are attacking somebody famous across any and all of our wikis. An editor needs to watch a single page related to that famous person on each of 200 wikis - the biography in various language Wikipedias, the Commons image, the Wikidata item, maybe even a page in several languages of Wikiquote.

Perhaps this is too ambitious for a grant-project? If so, then this important core-infrastructure work should not have been offloaded as a grant project.

This task is about *only* the discovery of the global watchlist and learning how to use it, *not* the ability to include all wikis with watched pages (for a number of reasons: there is a site limit, and your watchlist automatically includes your own user and user talk pages)

Currently, the only places to discover the global watchlist (as far as I can tell) are all only on the central wiki (meta in this case)

• in preferences, it says that preferences for the global watchlist are configured separately
• in Special:SpecialPages both Special:GlobalWatchlist and Special:GlobalWatchlistSettings are included
• in Special:Watchlist there is a sidebar link to Special:GlobalWatchlist

Ideally, we would also have a sidebar link to Special:GlobalWatchlist (on the central wiki) being displayed on Special:Watchlist on the other wikis, but

• how do we get it there? The GlobalWatchlist extension is only deployed on the central wiki. If we deploy it elsewhere just to add a link, it'll need to be configurable to not register its ResourceLoader modules or special pages, and to have a slightly different link target
• what should the default behavior be when arriving at Special:GlobalWatchlist from a non-central wiki? The default behavior is currently to only include your watchlist on the central wiki, but for users that are not active on that central wiki this isn't as helpful

@Alsee would you mind clarifying what you would expect the behavior to be? Maybe we should create a survey or something. If the user already has settings configured, we should use those, but if not, include just the non-central wiki that they arrived from? Include both that non-central wiki, and the central one?