I'm confused by why any of this is needed?
So you want to have 3 screens, side by side. Start with the left-most screen, then move the camera so that it's on the center screen, then on the right screen, correct? So what difficulty are you running into? Nothing is preventing you from moving the UI camera around. As long as you don't anchor anything, you're fine. Even if you do anchor something, use "Offset By Anchors" option on the panels, and move the panels instead of the camera. In your case I wouldn't anchor anything just to make it easier.