[tom_]

dear imgui is versatile in that it can be used in the sorts of programs that haven't traditionally been well served by existing desktop GUI libraries. (It also has a very convenient API that means you can cobble these GUIs together much more quickly than with most other libraries. So that's helpful too.)

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.)