If you log into your Activity page and find the "Action" list box gives you no option to edit your waiver, like the example below, then your recommender has already started the form:
If the recommendation is complete, the "Action" button will instead be grayed out and inactive:
If you have already submitted your application and your recommender's status reads “Completed!” you will not be able to change your waiver.
However, if your application is unsubmitted or your recommender has not completed the recommendation form, you can still waive your right to view if your recommender is willing to restart their recommendation.