Unread filter for Activity notifications

"unread" option on "activity" notifications

Add an "unread" filter to the Activity notifications tab, matching the filters already available on the For You and Mentions tabs. From one of my members:

“When you get notifications , you can sort by For You / Mentions / Activity.... on the first two I can filter out and see the ones that are "unread" is there anyway to add that same filter on the Activity notifications as well. I don't find that "mark all as read" always works either so I end up chasing myself to look for unread ones just to clear the red dot!”