For some reason, Disney has removed the ability to modify an existing dining reservation through the My Disney Experience mobile app.
Before the change, guests could modify a reservation via the app up to 30 minutes before the reservation. The app would allow you to move the reservation to another available date and time and adjust party size based on availability.
Guests would have to call to modify or visit the restaurant if it was within 30 minutes of the reservation.
As you can see, the app now instructs guests that they will need to visit DisneyWorld.com to modify an existing reservation. Weirdly enough, the cancellation option remains in the app.
There’s no word from Disney as to why this change was made at this time.