OS X 10.10 or later. iTunes only allows one playlist to be selected at a time. This applet can perform common useful tasks on a multiple selection of playlists: rename (add text, remove text, search and replace text), duplicate, delete, export, merge.
Tools in the Rename tab operate on the selected playlists' names
(via in-app purchase)
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Recreate a playlist such that its visible columns mirror the Music library
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Perform tasks on a batch of playlists; rename, delete, duplicate, merge, more
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Delete characters from the beginning or ending of selected tracks' name, artist, album, comments, composer, or show tags
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Create a playlist for each entry of a specified tag
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Exports and then re-imports selected tracks' artwork