The user should be able to see (like on Windows) if a folder is empty without opening it. This has been a a user request for large folder structures for cleaning up empty folders. This has regressed in 2020.1.

Showing a special icon for open folders does not provide any extra information as we already have the expanded arrow that indicates this in the folder tree.

The regression was introduced in this PR https://ono.unity3d.com/unity/unity/pull-request/91765/_/editor/bugfix-1176784