I have an ergonomic support for my right arm. My elbow rests on a silk fabric "hammock", which is supported by a linear bearing slide, mounted on a vertical shaft. I bought it too many years ago to remember a brand. And hopefully the description makes sense.

Basically, my right arm feels ~weightless.

Edit: Also, I use a touchpad, not a mouse. If I use a mouse, my hand cramps. And it also helps, I think, that I never learned to type. So I've developed my own style that doesn't hurt me.