I prefer to take frequent walks, which also helps to clear my head and forces me to do other exercises like climbing stairs. A “standing desk” just seems like a really complex solution that doesn’t even address any part of the problem except the sitting. Also, standing desks are really weird in a cubicle situation where suddenly your neighbor is towering over the wall for an hour, peering into your space.
Other times, I do focus for a longer period of time.
I have a multi-monitor setup in my office but these days, I mostly work on a laptop that I'll take to different rooms around the house.