They are perfectly suitable for regular app. You don't need to update them at 60fps, you have the entire control of the rendering state, so you could decide to update the gui whenever it is needed and not at a constant fps.

The common solution is to only update rendering when input happens, and otherwise sleep. That's fairly common for ImGui applications outside games (in games it doesn't make sense of course, since those usually render each frame anyway).

You can update when you want and only on changes if it works better for your case.

I think Nuklear had an option for dynamic update rate. Not sure though