I accidentally clicked on the blue button to mark all as read above the blue button to mark only the most recent notification as read. I also can't see the notifications anymore under "All notifications". Is there a way to undo that marking or see the items most recently marked as read?
Topic on Help talk:Notifications
There is not a way to undo that, but you can see the page Special:Notifications at each individual wiki to see any that were cross-wiki notifications.
Okay. Maybe showing a "undo mark all as read" there would be possible and/or not showing the same blue mark as read button just above the mark item as read while looking exactly the same (e.g. rather differently at the bottom).