There seems to be a similar entry in the ToDos - "when a user types in a absolute path that is not indexed, add it to the temp index?, ie user types \\tv\ which is not indexed, so we grab just the folders in \\tv\, that way we could quickly paste something in \\tv\uploads without it being in the index.."
I'm supposing equally there could be a File - Open Folder... menu and tickbox for durability, and corresponding ability to remove the folder if not session-transient. The main thing here is convenience, something fast, obvious and simple without lots of options.
I suppose these would typically be network folders, external memory cards, dvds and external drives or ad-hoc ram drives.
There's currently also the File List Editor which can have folders added for a direct view but lacks the tree view and other paraphernalia and also the theme that's been set up on the main results view.
When you're using Everything for everything, it's convenient not to have to switch to Explorer to do such tasks. The whole idea in using Everything could in fact be said to be never to have to look at Explorer ever again
D