I've just posted a new Create Kindle Collections plugin for Calibre at
https://www.mobileread.com/forums/sho...d.php?t=118635
Its still new, but if you want to try it, feel free to head over to the link, download it and post comments in that thread.
I started it after reading this thread and seeing that development had stopped. I've taken a slightly different approach in that I ignore the existing collections on the Kindle since I just want to use Calibre as the source data so it might not be for everyone.