The ability to create "Virtual Folders" including (or excluding) files/folders that match certain criteria:

-Files/folders defined by the user.
-Files/folders with specific TAGs/Metadata
-Files/folders with specific strings on their name.
-Files with specific words "inside" the file.
-Files with specific filetypes (.jpg, .png, .pdf ...)
-Files belonging to some "group" (images, videos, documents...)
-(other possible options to consider...)
And of course, a combination of the above...

Some OSes have something like this (saved searches), but it is somewhat limited...