[nh2]

I don't think so: Full immediate mode rendering on the GPU would require scene graph and application logic on the GPU.

People don't do that stuff in shaders or CUDA, because they were neither designed for it, nor is it fast, nor is it pleasant to code.

[bdowling]

An immediate mode GUI doesn't have to use immediate mode rendering. For example, the Dear ImGui library "outputs optimized vertex buffers that you can render anytime in your 3D-pipeline enabled application." [0]

[0] https://github.com/ocornut/imgui