I am happy to report that we just released version 2.3.2 with the long awaited folder support for the Design panel! The folder structure is preserved when exporting and previewing your designs, allowing you to structure your websites better.
The folder support required a lot of changes to the code base, and it is possible that a bug or two have slipped through. Give the update a try, and if you run into something we've missed, be sure to report it here. We will fix it with the next minor release.
Looking forward to your feedback :)