"Folder only" view in Outliner

It would be useful to have a HIDE FILEs button in Outliner.

Here’s why:

Some of us use a deeper structure than just chapters and scenes. Some “Files” may end up belonging to a higher level Folder, e.g An “Overview” might belong to a Section level folder, and be at the same logical level as the Chapters, but not have the same structural significance.

A problem with the outliner is that when the “filter” feature is active, no hierarchy is shown anymore.

It would be great to see all the folders and files with their structure, but filtering out some labels, or types (folders etc.)

Actually, Corkboard Timeline View does this, so folder only probably not needed.