Interestingly, I tried to use the "modify" trick yesterday on an upcoming Aulani stay (within 60 days) to swap in 18 of my points in holding (16 of which were tied to a Riviera contract, 2 of which were OTU points). I couldn't do it online as my BLT contract was "locked" at the top and therefore it wouldn't pick up the points in holding listed second and third. (The BLT contract shouldn't have been locked, as I didn't use it for home resort 11 month booking for Aulani, obviously.)
I thought I'd be out of luck given MS sometimes refuses to change it for you, but I chatted with a nice CM from MS who very quickly swapped in my holding points, freeing up 18 points that I could bank into 2025.
YMMV, but thought it was interesting that I could chat to get it done. I'd read anecdotes that sometimes MS on the phone won't do it for you, so always best to try it online myself first. But if it won't let you for some reason, always worth a chat/phone call.