Undoing the last call once the auction has finished (Realbridge).
Just an update on this. On RealBridge, the Director can now undo the last call even if the auction has finished. In fact they can undo all the way back to the beginning of the auction from just before the play of the very last card.
You'd never want to do that in a proper game but you might for teaching "Let's see what would have happened if you'd opened 1H instead".