Service to expose entities to Assist / Google Assistant

[TheFes]

With Christmas coming up, it would be nice if it was possible to have a service call to expose entities to Assist /Google Assistant.
So when I enable input_boolean.christmas I can immediately turn on the Christmas tree using voice.

I do realize this is already possible by hiding the Christmas related entities. But in other use cases it might be nice to keep the entity visible and not expose them sometimes.