BigGuyRunning unfortunately you can't - you can only reschedule runs up to and including the day that they are scheduled for and there is no real facility to reschedule the whole plan although it does let you move the race date which effectively reschedules
You could Pause the plan though, were you able to run the workout in between scheduled runs. Just check what the excercise was and make your own or duplicate the same in the App.
I’ve got now a notification on not being able to reschedule my Race at the end of a plan though. It says, that something went wrong, but the culprit is with Garmin Coach.
