The ability to easily delete notifications would be a boon. I found the "mark as read" once then, on returning all I find is "view more". This choice repeats till end of the listing of notifications.
That's what I was referencing. They should leave the list when you click them and if you use the "mark all as read" button, they should all leave the page, but not until you refresh the page or leave and come back. There is no button for individual notifications.