Literally all of them are using it as part of non-user-facing debug tools for 3D graphics:
https://github.com/ocornut/imgui/wiki/Software-using-dear-im...
Meta as part of their VR/gaming division, Google in their VR division and 3D rendering engine, Ikea in a 3D material editor, and Intel in a 3D SDK.
And again, the intended use is immediately explained on the project repo no matter what the comment you were replying to said.