Add any item in the tree to your Favorites, including "My Computer" folders, playlists, view schemes, and purchases by clicking on View > Navigation > Add to Favorites while in that view.
Your favorites will now appear at the top of the Navigation sub-menu.
To organize your Favorites, go to View > Navigation > Organize Favorites.
We recommend adding the "Navigation" toolbar button (right click on the toolbar space to customize the toolbar) if you use these often. Then you have quick access to your favorites.