Many tree-based UI's allow you to temporarily set a particular node as the top of the tree, so that searching, filtering, and navigating around are focused on that area. 

We have one folder with a large number of protocols that is 3 branches down from the top level Protocols folder. I would love to be able to pin that folder as the top and hide the whole rest of the tree while working with those protocols for ease in navigation. I would even more love to be able to pin as the top the contained folders dedicated to individual applications when working with those applications.