Notification - Read and Unread

Currently all notification remain, with the same time stamp whether they were created 1, 2, 20 days ago. After clicking and reading the notification, the status does not change in the notification pane.
It would be great if notifications had accurate time stamps, but also had a status such as new, read, high priority or other. Currently, we can only clear all notifications, which is helpful but not an ideal solution. There are no ways to view old notifications, so instead of clearing them I would prefer to have a ‘Mark as read’ type of functionality so that I may go back and reclick a notification that I want to revisit.