Hide folders without active tasks/projects

Currently, when inside a space, you can filter the left sidebar by showing "All" or "Only Active" projects. Since I use folders within a space to represent each client I have, the list of folders get LONG. It would be awesome to have a way to filter by folder, not just project.

The filter would allow you to only see folders that have an active task or an active project within them. This way, you can see only folders associated with something you are working on. Now I understand you can create a widget for active projects, but folders filtering would be cool too.