Choose an item or folder in you library (not double clicking, just a single clisk to highlight), then go to the top of the library palette and right click, a drop down menu will appear and you'll see "add to collection" (or create new collection) click on it, name the collection and there you go.  Now whenever you want that item or folder, just go to the collection usign the same method to find it.

I haven't doen it yet, so I don't know if it's working, but I did find the option and mentally noted it.

It does not (btw) change anythign in your runtime locations, it just creates a new path for qucily finding things.