How to get some variation in position

I have a nice work set up at home with an adjustable desk, external monitor, ergonomic keyboard and armrests. However this set up require me to sit in a very similar position all day. I would like more variation, maybe even switch location in my home, but I get back pain unless I use an ergonomic set up.

One option is to stand more but I get tired in my legs very quickly, I’ve always had trouble with pain in my legs when standing. Even if I use a softer standing mat. So if anyone has some advice either how to be able to stand more or of different ways to mix up my work set up I’d be grateful.