Wouldn't it be nice if you could navigate to an item (i.e. a tag) in the Library Tree without having to expand all of the 'branches' that contain it?
Well, sometimes, you can!
Take the Tag Cloud, for example. Hopefully, you all know that you can left-click on an item in the cloud in order to create a new search on that item (and, of course, clicking whilst holding down CTRL, SHIFT or ALT allows you to filter-in, filter-out or append, respectively). Well, guess what happens when you right-click on an item? You're way ahead of me, right? And you'd be correct: The Library Tree expands to reveal (and select) that Tag.
Also, you will be aware that the Browser context menu (the one that appears when you right-click on a thumbnail) has a 'Find Similar Files' option, that lists all the Tags attached to the related file. Left-click behaviour on any of those Tags is exactly as described above for the Tag Cloud. And (you guessed it, again) the same is true for right-click behaviour.
So there you are. Two ways, using a right-click, of automatically revealing and selecting a Tag in the Library Tree. Enjoy...