Only shift the future workouts, start on the day or week and use the menu to shift the future ones “on date and after” by the number of days/weeks you want to move them. Keep in mind though that these plans expect you to be following them so giving yourself break weeks or shifting things around can have unintended consequences for starting back, you might not be where the plan “thinks” you are in terms of readiness. Another option to repeat weeks is to reapply the plan on later weeks and move the weeks you want back to now, or copy the completed + future weeks and paste them into upcoming days.