I know that you can mark all as read. But is there a way to mark notifications so what you have read is not shown in the notifications menu when you click on you profile picture in the sticky header. This only holds 17 or so notifications (or lines). You have to click on the arrow at the bottom to go to all notifications and see the ones that are not yet read or did make it onto the notification list in the profile picture menu.
Pressing dismiss all in the notifications area on your profile only seems to mark all as read but it does not clear the notifications menu. It would be nice if Discourse removed those notifications after being clicked on or clear the menu on the stick header (profile picture).