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If it's got an accessible screw/fixing holding it in place from the inside, or on the edge where the locking action happens, back that off a bit and give it a squirt of something oily.
Nothing is accessible sadly, the most I could do I think would be to remove the handle, but the stuck pin is ~35cm horizontally from the handle.
Dammit-
the LEAST I could do I think would be to remove the handle
I'd say it's a 25% chance of success with simply removing the handle and pushing the gearbox across by itself.
More often than not, the hole that the gearbox sits in isn't long enough to fully unlock it Or the rod is no longer attached to the gearbox.At around 70cm across, there should be enough flex without removing the glass, to push the working end outwards 20mm or so, to clear the keeper plates and then lever the window across.
user69121
If it's got an accessible screw/fixing holding it in place from the inside, or on the edge where the locking action happens, back that off a bit and give it a squirt of something oily.