How to Test CAMERA_FEEDBACK?

I would like to test the camera feedback function on the bench. I have read that a green camera symbol is shown when feedback is received but I can’t find anywhere in the documentation that mentions it so I am unsure where to look for it. Have been through as many menus as I can find to try and enable it.
So I am wondering if you only see it on your grid when flying a survey mission?
Is there a way to make the HUD flash or a camera symbol display in the HUD? So it can be tested on the bench or preflight to confirm it is working using Camera Trigger Now function? Or is that already a thing and my rig is not working properly?! I really don’t want to have to make a flight and download logs to find out if it works… It seems a rather long way to go about it and my prototype circuit is still in the testing phase!