You can reschedule a workout from any Stryd training plan with the Stryd app on your phone and PowerCenter. After you rescheduled the workout, you may need to fetch the workouts again on your watch to remove the session from the watch.

In the Stryd app, long-pressing the card for the workout you want to reschedule (same for iOS and Android:

After selecting Reschedule, you will be able to pick another day to do your workout.

You can do the same in PowerCenter by simply dragging the workout card to the day you would like to do the workout.