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Take off the interior tailgate panel, reach around to the driver side hinge, unplug the sensor, and short the 2 wire connector with a wire (preferably with 1/4" spades attached, but for the short time a wire will do). I've been doing this for years.
I have done this on many occasions when the window failed to go all the way up due to rust and lack of lubrication.
All you need to do is latch the drivers side latch while the tailgate is in the down position. This fools the tailgate closed sensing switch and allows you to actuate the window up and down using the key in the tailgate.
It has been a while since I have done this, however it think it will get you started. Just remember to un latch it and have your window down prior to closing. Also a good idea to have someone support the window if the gate is down and the window is fully extended.