I love this program. I hope this is the right place for suggestions. Without bloating the program too much it would be great to:
1) Be able to use alternate keys for entering "possible numbers" (PN) (Shift+1..Shift+9). I would like to be able to use either the keypad 1..9 to be PNs, or even QWEASDZXC as 789456123 (mimicking numpad) or QWERTYUIO as 123456789 (the row just below 123456789). That way I wouldn't need that infernal Shift key pressed. Alternatively, allow CAPSLOCK on to signal PNs.
2) Undo last action(s) (e.g., Alt+Z or "U").
3) Allow Branching by Saving current board and Restoring to that state