Remove the door panel
It wasn't 'till I dropped the glass, that I then saw and heard the problem, here.
It was this large washer. It holds the glass in place against that part of the riser. The screw was loose, and the white nylon piece was rattling against the glass and the plated washer. I had to remove it to find the right sized Torx bit.
I could just get my hand back here to screw in the screw by hand, then I put the bit in the socket,m and turned it using a small crescent wrench. No pics, 'cuz my hands were full. but it works - no noise now. BTW- These highlighted spots here are the white Delrin guides for the window lift. A good lube of silicon spray or a WD-40 look-alike LPS-3 will stop all squealing windows.