In earlier versions of Apple OSes, you could edit the menus yourself, with the officially supplied resource file editor app and there was nothing really special about it.

There are `ibtool` and `plutil` CLI commands built-in to macOS these days too, but to get some graphical editor, u would need to download 3GB of Xcode and u would invalidate the code signatures, etc...

Plus there is a huge churn in the application versions, so any customizations would need to be applied repeatedly to newer app versions.

Sad, really...