Currently, Plexamp does not allow you to view or edit album ratings. You have to go to the “main” Plex app to do so. This seems like an easy and valuable thing to add to Plexamp.
This has been suggested before, by the way: View/edit album ratings in Plexamp (my original suggestion, then someone told me about Feature Suggestions)
We need this and if I might add, album ratings should have the same rating options already available for songs: one star, five stars and five stars with halves.
