If you want to change up your iTunes playlists, you can delete items from playlists while still keeping them in your library. When you delete an item from a playlist, the item is simply deleted from the list — not from the library. You can also delete entire playlists and this also does not delete or change the content in the library. Note: Switch to the Library sections (Music, Movies, TV Shows, and so on) in the Source pane to delete items from your library.

To delete an item from a playlist, select the playlist in the Source pane and then select the item. Press Delete/Backspace or choose Edit→Delete. In the warning dialog that appears, click Remove to remove the selected item from the list.

You can also completely delete an item from your library from within a playlist by selecting the item and pressing Command+Option+Delete (Mac) or Ctrl+Alt+Backspace (Windows).

To delete a whole playlist, select the playlist in the Source pane and then press Delete/Backspace or choose Edit→Delete.