If you organize your iTunes playlists into folders and subfolders and sub-subfolders, then you’ll probably find these simple tips useful. As you’re well aware, a folder with items within it shows with a small triangle to the left of its name, indicating it can be expanded by clicking on that triangle. Once expanded, clicking again will collapse that folder.
If you hold Option while clicking on any folder’s triangle, you’ll expand (or collapse) not only the selected folder, but every subfolder within it, along with any other sub-folders, etc., all the way down through the tree. So with one click, you can see (or hide) everything within a given folder. This behavior mimics the Finder, where the Option-click trick does the exact same thing.
This second shortcut, though, doesn’t have a counterpart in the Finder. If you Command-click on a folder’s expansion triangle, you’ll see that all folders at the same level as the clicked folder will expand (or collapse). Note that this action will not affect subfolders; if they were open when you collapsed all folders, for instance, those subfolders will still be open when you reopen the parent folder. But if you’ve been drilling down into your folder structure and want to just quickly get things looking nice and neat again, just Command-click on the parent folder and things will instantly look much cleaner.
Now if they only had a similar shortcut that would work on the piles of stuff on my desk.