How do I modify my reservation to reduce my stay at a Disney Resort by 1 night?

If I need to cut one day off of the end of my trip at an on-site resort (ie check out on Friday instead of Saturday), how complicated is that? I would be making the change at least 7 months in advance so no interference with ADR or FP.

Do I just call Disney to make a modification to my existing reservation? Or do I have to cancel the existing res and then make a new one (and thereby risk not getting the room category back if someone else swoops in and grabs it)?

I called. Every time I tried to do it online it said it couldn’t. So I called and they fixed in a few minutes.

I recommend calling for any modifications. Or for booking something that is complicated like multiple rooms, split stay, occupancy issues (party + infant), etc. Often rooms will appear unavailable but will magically be available when you call.