Treeview option for Folder Portals

How difficult would it be to add 'folder expanders' to the individual folders in a folder portal?

I use a folder portal for a work folder that I access frequently,  that I keep  next to notepad++.

The folder/filename list the portal presents is great, I would just love to see it listed in tree form, keeping the other open folders with file lists in view.

Unless I'm missing something obvious, I don't see that as an option.