When opening a Debug Window, it is possible to skip the loading of any expressions that have been saved within the Custom Watch Pane by holding down the shift key.

This will cause all previously input expressions to not be loaded into the Custom Watch Pane. At this point, if you do not click Save Settings while that Debug Window is open, then the previously saved expressions will be loaded upon the next normal opening of the Debug Window. If, however, you click Save Settings while the Debug Window is still open, then, as usual, whatever new expressions have been input (if any) will be saved and loaded when the Debug Window is next opened.