Even if they could use just the two LEDs at either end, that would be useful. There's one above the camera that I've never seen lit on my Cosmo, but I do recall seeing it on in a Cosmo video (can't recall which).
Maybe they can come up with something clever that uses those two at either end plus the two on the fingerprint / rocker switch, but as those two are taken over by the cover display, I don't know if the two can play nicely together.
Put it in airplane mode from android main screen and then close the device. The only way I could trigger it and see if it works (and exists at all). It should light red in that case scenario and doesn't turns off even if ext. screen goes to sleep. Puting device in airplane mode from external screen doesn't trigger it at all. I made both recent firmware upgrades (android and codi), if that matters. Must admit I did't even knew it's there... OT: I think 4 leds, in some kind of cross geometry, are definitely enough to be used smart without any help from external screen (IMHO), in some sort of high power saving mode when batt. level is under 10%, or similar. All of this is very low priority to PC at this point, actually, it sounds like something for community to handle at some point...