Godot uses their own engine features for the GUI of the editor itself as you’d use to make a game itself with.

https://docs.godotengine.org/en/stable/about/list_of_feature...

> Godot's GUI is built using the same Control nodes used to make games in Godot. The editor UI can easily be extended in many ways using add-ons.

And they even go as far as to explicitly say the following:

> Godot's small distribution size can make it a suitable alternative to frameworks like Electron or Qt.

I’ve only used Godot for game development, not GUI stuff yet. (The game I started making doesn’t have any menus, I’m working on gameplay and level design first.) But I’m personally keeping a mental note in the back of my mind to investigate building bona fide desktop applications with Godot also, and not just games.

Also, if you’re going to make an application instead of a game, they have a special mode they recommend that you use:

> When creating a non-game application, make sure to enable low-processor mode in the Project Settings to decrease CPU and GPU usage.

https://docs.godotengine.org/en/stable/about/faq.html#is-it-...