UPDATED: Playlist Manager v1.1
Playlist Manager v1.1 can perform common useful tasks on a multiple selection of playlists: rename (add text, remove text, search and replace text), toggle repeat and shuffle, duplicate, delete, export, merge.
This latest version fixes a problem with renaming playlists that are contained in Playlist Folders and now allows "blank" to be used as the replace text in the Search and Replace tool.