You can create a program for that zone, and just set any time and weekdays. As I said, make that program ‘disabled’ (i.e. not enabled), that way it doesn’t run normally (hence the time and weekdays don’t matter), but it can still be triggered using the program switch. It needs to be the first program because the program switch only triggers the first program, but again, it’s disabled so it doesn’t run unless if you trigger the program switch.