Actually, globalProperties is a compatibility API, and I don't recommend using it. As you said, you can set global variables through the window, but you can write a hook function or use a library like Pinia to manage your global state and global variables.

Another point worth mentioning is that getCurrentInstance was a public API provided in earlier versions. It was used to retrieve the current component instance, which in turn allowed access to the app context. However, due to stability considerations, this API is no longer publicly available and is no longer mentioned in the official documentation. Therefore, I strongly recommend that if you are using setup to write Vue components, you can use other methods to set global variables; globalProperties is not mandatory.