Improvement - Option To Nest Folders as Sub Folder Under a Main Folder / Heading

I would like to see an option to mark folders under Main Folder so that we can expand and see the sub folders whenever we need.

Because at present I am seeing all folders which stays as it is and which consumes more space instead if we have some + or - button in the main folder so that the sub folders are getting hidden under the main folder like that. So the view which will seems to be the one we see in Windows Explorer when we enable Folder View .