I was informed with these specific points, they would not allow you to modify to use the older points first without a cancel and rebook situation. I had planned on trying to grab a few nights in October with my current UY points and then swap out the points with the banked 2018 ones in early June because in the past, we've done something similar. I was told that for this instance in relation to COVID19 that the 2018 banked points with the Nov. 30th extension would only be able to be used after the following:
1. disappear from your dashboard which is a notification that they have been banked by
DVC
2. you must call in to book
3. they can only be used on new reservations.
If someone finds out something else, please let me know! I'd be happy to grab what I need now and then swap out to use the older points later.