Collapse all folders (button or hotkey)

After having SmartFTP open a couple hours/days, my folder tree starts to get very long.
Right now I just close and open the program, which resets my folder tree.
I was wondering if SmartFTP can implement a hotkey or a button to "collapse all folders". That would be really nice  :D

It does not make much sense to add a hotkey for a very special and mostly unused function. You can simply double click on the root folder and it will toggle the expanded/collapsed state.