A custom ViewModelStore shared between screens of a feature, but a smaller scope than Activity, but a larger scope than Fragment?

I think that is a great idea — and for some reason I didn’t think of it, even though it is a great idea.

Indeed, you could easily create your own ViewModelStoreOwner implementation. As long as the ViewModelStore is kept alive across config changes (retained fragment or onRetainCustomNonConfigurationInstance), it’d work.