This is how Peepso notification toolbar looks like, there are some functionality you may like.
Click "Show Unread Only" button to show only unread notifications.
Popover Notification box will show unread notifications only.
Click "Show All" button to show all notifications back again.
And If you don't want to read them all one by one, just click "Mark All as Read" button
Then your notifications now has marked all as read.