Remove the door
It's a mystery how baking slop gets deposited between oven door glass panels. But it's clear that you can't remove it without disassembling the door. The job's not that hard and takes less than an hour.
Remove the oven door (consult the manual for how to unlock the hinges and lift the door off). Then remove the exterior trim panel (Photo 1) and the glass hold-downs (Photo 2). Lift out the glass and handle it carefully (it's expensive and breaks easily!).
Clean off the crud with a nylon scrub pad, hot water and degreaser. Rinse and dry, then clean with glass cleaner. Wear gloves to prevent fingerprints as you place the glass back onto the oven door. Be sure the glass sits inside the locating tabs before you reassemble the hold-downs. Then install the hold-down channels and screws and the trim panel. Put the door on the oven.