Exactly. Trump should start sitting down, then announce that he's more comfortable standing, and invite Joe to do the same, if he'd like.
The “moderators” would never allow Trump to do that. They are there to make Trump look bad and this would play right into their hands.
He needs to insist on both of them standing. But he probably won’t.
It would have to be an absolute ambush on stage live or it won’t work.
If he announces it before hand they will short circuit it.