OS X 10.8 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
Displays files in iTunes Media folder not in iTunes track library
Two scripts copy text from clipboard to current or single selected track's lyrics tag
Add or subtract a user-entered number from each selected track's Plays
Stop iTunes after current track is finished playing
Remove iTunes tracks disassociated from files
Applet assists with swapping, copying, appending data between track tags