I used Godot to make a tool that was not really a game at all, and I read about others doing that as well. It works great just as a simple WYSIWYG GUI editor and GDScript is not a bad scripting language.
https://docs.godotengine.org/en/3.1/getting_started/step_by_...
https://docs.godotengine.org/en/stable/tutorials/ui/index.ht...
Here's an overview of what's available: https://docs.godotengine.org/en/stable/tutorials/ui/index.ht...