“Yes, totally. This is how you create oval shaped copper around pins, or funny shaped pads (e.g. square at one end and round at the other) by overlapping two or more pads.”
Simply add a pad on top of your pin and give them the same pin-number. If the soldermask is kept off both pins, and they overlap, they should appear as one pin on your board.
“Odd as it sounds, this can be necessary for some edge connectors. … but how do you do it???”
pcb_tips covers a lot of Footprint material. This page and that page need to be reconciled!