I wrote the Kindle Collection Manager many years ago to add missing functionality to the Amazon Kindle range of eBook readers.
It’s a Windows desktop app that allows books to be arranged into collections – both manually and automatically based on folders – then the collection configuration is uploaded to the Kindle device.
Unfortunately Amazon locked down the file system on all devices from the Paperwhite onward which renders the app unusable.
For owners of previous versions of the Kindle eBook reader where the collections.json file is still accessible over USB, the KCM will still work.
Here’s a link to download the last version that was released.