It look like button gestures the ability to rotate the screen from good lock module , you can add short cuts to your button navigation or it's the Android auto rotate feature.I'm trying to understand that screenshot -- do you have splitscreen turned on? Also, you said tapping it wakes the screen -- so it's visible even when the screen is asleep?
Understand but we going need more feedback to figure it out but to me it looks like what I describedMy husband is a phone noob. And has no idea. He is currently working in USA and I am in Cape town South Africa. That is just the screen shot he sent. Doesn't have time to press on it