+1 for this feature as well, the recent files tab is fine, but it makes things kind of messy, especially if you're working on multiple projects. The songs tab is unreliable (to me, at least) since I use other places outside of Studio One root folder for Songs, and I'm sure many other people do it too.
I don't think it's hard to implement and it would greatly improve organization for everyone. If you want to take it a step further, the answers to this post also give great thought on how to make it even better (tags/colors/etc) but I'd be happy with the base filesystem of the user drives and remembering the last folders the user had opened.