Special:Notifications has buttons for "All Read Unread" at the top. But it has no information for cross-wiki notifications. Perhaps that should be added as an option?
Topic on Talk:Notifications
Right, as Quiddity points out below, we do have that feature. But you can access a given remote wiki from the Notifications page only when you have unread notifications on that remote wiki. @WhatamIdoing, is that good enough? Or were you wanting something more?
That's phab:T129366 ("List wikis and pages with unread notifications in the Notification Page left nav") - see task for mockups, and ongoing work. :-)
I want access to the "already read" notifications without having to go back to the original wiki.
So, doing that systematically and thoroughly—offering links to all the wikis where a user ever had a notification — isn't as simple as it sounds, since the infrastructure for cross-wiki was developed with the idea of bringing unread notifications to the panels. And the resulting list of wikis might be quite long for some of the people who would actually use this. But a cheat might be possible that would, for example, show all the wikis on which you'd had notifications in the last X days.
Still, even that would involve some thinking and work. In our user tests, we didn't see evidence that users have a lot of interest in going back to find old notifications. When asked to detail a time where they'd had to do so, most users answered with a variation on "Ummmm."
Can you perhaps lay out a few common scenarios in which people would have a need to check wikis where they have no new notifications?
The scenario that is most important to me is this one: I got pinged when someone copied a message to multiple wikis, and now I need to check those messages (e.g., to see whether anyone replied later). Here's a recent example: Right now, the only ways to find those messages are either to have a particularly good memory (the method I used here), or to check dozens of wikis until I believe that I've found them all (the method I probably should be using, because there might have been four of those discussions rather than three).
Just thinking, but what if you had a way to select wikis you wanted to bring up on the page? Like an autocomplete box that would let you mount wikis you want to look at? Might that be a good way to do it, instead of making the system keep track of all your activity? It would be a manual process, but you could stay on the same page.
Sure, that would be fine, if I could quickly click through a list of all the options. (Well, in the worst-case scenario, it wouldn't be quick, because there are 800+ of options, but only 200+ that could be pinging me in this account.)
Could it give me a short list of the places I've gotten pings from most recently/most often? Even the top 10 would probably be adequate for most situations. (I do need it to cover more than just different languages of Wikipedia, so the exact approach used in Compact Language Links wouldn't work.)