Tag a Location inside an Instance

I want to propose a feature to mark a spot which is then pin pointed by the Map.
Maybe an arrow directs you once out of the scope of current view.

But the most important property would be to be notified during an area-to-area transition that there still is a tag left in the area which was recently vacated.

Scenario:
I enjoy to fully clear maps and sometimes "forget" about a strongbox, Master-Quest or what ever I spared at first glance.
Generally there is a flash of recollection after the Instance idled out.

(I hope this is not a duplication - a quick forum search came up empty)

Best Regards

Any thoughts, comments?
...is there a demand or is this just a noob idea?