I've been talking to my manager about this. The problem is, after moving to an open floor plan, paradoxically we don't have room anymore.

I'm trying to work standing up for a bit. It does help, but of course is far from ergonomic at a regular desk. It probably also looks ridiculous, me doing a semi-split to get low enough to reach the keyboard and mouse.

Try using a few reams of copy paper (or books and boxes etc) to prop up monitors and input devices. I had such a makeshift setup at first.

Also, have you tried working from home? Orthogonally, negotiating a four day work week 4x8h (at 80% pay) might help you enjoy yourself more. Managment might not be too happy, but if you insist and tell them that the alternative is 0 day work week at 0% pay (i.e. you leave), they might see the light.