There is no easy way to to favourite an album, even when in releases view.
It probably should be implemented in multiple ways, in menu toolbar, 3Dots menu...
But if I could ask for one implementation, I would like to click in the heart icon of any album. All the time, in all views.
The same is valid for rating albums.
Set favourite is planned/under test.
Rating will not be implmented now since it is more complex and involves tagging.