The trim handle is a circa 1950's automobile window crank handle and it does come off. If you push up on the overhead panel near the handle you will see a slot in which there is a clip which holds the handle on the shaft. There is a tool made to fit in the slot to push the clip out to release the handle. I suggest NAPA. It can be done with a screwdriver but the tool is much better and try not to push the clip all the way out. It will fly and be hard to find.
Don is right about the origins of the trim handle. The clip is a "U" shaped clip. The orientation is parallel with the handle, IIRC. I use a piece of welding rod bent into a hook, to reach in and pull the clip from the base. Once the clip comes out, you can pull the trim handle off. Slide the clip back into position in the handle, and then the handle can just be pushed back on the shaft. The clip will snap into position.