Thanks Vernski,
I don't have a picture available, but I did remove the door handle and window crank by removing the set screws. It is the screws on the armrest I was having issues with.
Here is a
picture of someone else's Chevy C10 with a similar door handle.
The screws that hold the armrest to the interior panel also go into the door itself. I was trying to get the interior panel off to do some window related work.
The manual showed pictures of the door handle and crank but not the armrests, so I wasn't sure if this was a stock door/panel or not. I think it might be a Chevy C10 replacement panel as in the picture.