That's really neat! ImGUI has got to be one of the most satisfying GUI libraries to use, its fast, versatile and looks absolutely beautiful, so spreading it to even weird places is great!
It's too focused on desktop (mouse/kb), and you can't really theme it other than its colors and shape of the edges, doesn't support animations and you can't style the font, it's pretty basic
Creating custom controls is a ton of work
Then you have libraries like this: https://lvgl.io/ (gh: https://github.com/lvgl/lvgl)
That's what i call a versatile GUI library
lvgl looks like something you'd use for making the UI for the actual product. dear imgui is for the debug tools that get stripped out of the version you release. It's not intended for user-facing use, so there's no significant support for anything visually interesting. (The actual appearance of the UI isn't really even all that important. It just has to be not too weird-looking.)
I never mentioned "limitation", ImGui is great for what it is, i wouldn't use lvgl to build my engine tools, i use ImGui actually