Playing the next best move
When ChessPartner plays a move from the opening book or end-game database it’s likely that there are more possible moves to play. That list of moves is sorted having the best on top. By selecting Next best from the menu or press Ctrl+Z the already played move is taken back and the next move in the list is placed on the board. That and consecutive next best moves have a lower score that the initial move. The list is circular, you may rotate through the next best moves till the first shows up again.
Next best is only available if there’s more than one move.