The main target of the Godot Engine are game developers. But Godot's easy workflow and functional UI elements, makes it also a good fit for non-game applications. There are already some out there you may know, like Pixelorama, an Open Source 2D sprite editor.
Without much experience building UIs aside from web, my limited experience with Godot leads me to believe that building an application this way would lead to a lot of decentralization of logic, which might be a bad thing for complex applications. For example, various UI elements might have a bunch of logic attached to them instead of having a centralized place where the logic lives. I guess this happens in web too, and maybe native UI frameworks/toolkits?