Rename and delete
What a rename touches, what a delete takes with it, and how to check before you do either.
Renaming
Open the label from Labels and go to its Settings tab, or choose Rename from the menu on its row in the list.
A custom label stays attached to everything carrying it when you rename it. Nothing needs reassigning.
Screen labels can't be renamed directly. Rename the screen and its label follows. All Screens can't be renamed at all.
Deleting
From the label's Settings tab, or the menu on its row in Labels. The labels dialog also has a delete control against each label.
Deleting removes the label from every screen and playlist carrying it. Any playlist that was reaching screens only through that label stops reaching them.
Before you confirm, the dialog says what deleting will do: how many screens will stop playing how many playlists, or that nothing changes on any screen. Screens that also get those playlists through another label, or directly, aren't counted, because they keep playing them.
A delete can't be undone.
Check before deleting
Open the label from Labels. Its Screens tab lists the screens carrying it, and its Playlists tab lists the playlists it plays.
If the playlists list isn't empty, deleting the label takes those playlists off those screens. Retarget them first.
Tidying up
Labels accumulate. Campaign labels from last year, a site that closed, a typo nobody removed.
The Labels page shows the screen and playlist count for every label, which is the quickest way to find candidates.
Two rules make the clean-up safe. Delete a label only when it plays no playlists. And treat a label carried by no screens as a candidate rather than a certainty, because a playlist may still be targeting it and waiting for a screen that hasn't arrived yet.