Hiding notifications from online-accounts doesn't hide them all
I'm using Fedora with:
GNOME Shell 3.28.2
When you have a large number of notifications (at least when they come from an online-account), if you hit the clear notifications button they do not clear, some of them do, but the rest stay there and you have to hit clear multiple times, even when there is just a single page of notifications that should be cleared.