From my experience it is no longer possible to change the name online. When Hilton changed the system to this rolling tier plan the ability to edit the reservation name seemed to disappear as well. I'm able to add my name as the second guest but not have the reservation in my name.

We have a mutual account and only reward reservations in my spouses name may be made online. In order to reserve a reward in my name I must call - and even then I have to repeat several times that the name on the reward needs to be changed to mine.

If you find a way to do this online please let me know as I would love to know how and to be able to do this myself.