I have Xboard 4.9.1 running on my MacBook Pro with High Sierra. When I am in the Edit Position mode, the right mouse click does not work. In the older Windows version, I could clear a board, then right click on any square. That would bring up a menu of pieces I could place on that square. On my MacBook, any time I right click on a square, a White Pawn inserted there (e.g., see screen shot below).
Roy Prasad
