It looks like some of these create a module from within pcbnew. I just released a version of KiCommand that has unit tests for testing adding modules and pads. But nothing to directly integrate with the footprint editor.
Or I can find a footprint in a board. but I can’t manipulate a footprint through the footprint editor “board”. Apparently there’s no GetFootprintBoard() or anything similar, like there is GetBoard() for the opened pcb board?