One problem is that the bar stools are hard to get on and then move to be positioned properly.

Another problem is that leaning against the edge often doesn't work well, because a) the chair keeps slipping back and b) you rest your butt on a narrow edge which presses on nerves, blood vessels and bones, making it very uncomfortable.

I've tried lab stools, ironing chairs, bar stools, etc. and the problems are similar. Drafting chairs could work, but are too short for me - made for tall sitting desks (drafting table), not standing height.

I can think of two potentially comfortable solutions I haven't really tried yet:

1. A thick, padded round bar like they have on the London tube and other trains to lean against. This could be mounted on a wall, which eliminates the sliding away problem.

2. There are (expensive) saddle chairs - where you sit upright on a wide and split bicycle type seat that puts you at ergonomically healthier angles (135 degrees from thigh to back instead of 90 degrees of "normal" sitting). No leaning/slouching possible on those though. Further problem: Sitting on your reproductive organs for long hours may be uncomfortable and unhealthy.