There’s no easy way to “Mark all as read” for “All Shared Stories.” I think it would be great if there were one!
Sometimes you’ve got 150+ unread stories shared by the 25+ people you follow, and you want to declare Story Bankruptcy and mark them all as read in one fell swoop so you stop feeling guilty. Doing it on a person-by-person basis takes a while and makes you confront the faces of those whose shared stories you’re ignoring.