What is this Green marker?

Hello Devs, was wondering what this green marker is at the top right of my view in Studio, recently had a few objects fall from off of my shelf onto my keyboard, and pressed a load of keys, but I don’t recall ever seeing this pop up.

If you know what it is, please tell me how you get rid of it. Thank you.

check if it’s blue in play solo, it might be related to that viewport outline that tells you if you’re looking from the perspective of the server (green) or client (blue)

I’m not in play mode, but thanks though.