If you examine the contents of a Favorites folder you will find that it consists of a .png icon and a shortcut to the content from its original runtime.  This arrangement makes it easier to copy or move an entire Collections folder to another Poser version without breaking any pathways.  Creating additional subfolders externally will show up without any problems as I have demonstrated on a number of occasions.  Frankly, I think if you attempt to add actual content to that folder, it will not make it any different than one huge runtime folder.  Its purpose is to make it convenient to access often-used content from any runtime you're in without searching through the entire Library.  For example, I have a weight mapped V4 and her morphs shortcuts saved in my Favorites tab, this makes it easier for me to load her into my scenes if I happen to be in my Michael 4 runtime.  But you need to remember that the Favorites tab is just that, to save your most-used content for easy access.

Yeah, I agree a back button would be very convenient and practical.