I'm not sure what people mean when they say the "summary tab".
I'm not sure what people mean when the say "iCloud Library". I go to iCloud Drive on my phone and turn it on, but the word "library" doesn't appear.
The Genius did not appear above Music when I turned on cellular data.
So I still can't find the "sync" button, manually or automatically. I can't uncheck a song. I can't delete a song using the delete button. I'm stuck.
I finally found the sync button! I right clicked beneath the word Devices in the Playlists view and it came up.
maybe doing something in all those suggestions worked.