[kovidgoyal]

I've already implemented support for displaying the collections made on the Kindle when you connect it to calibre. There appears to be no way to actually create/edit/delete collections using the USB connection. Here are my notes on the subject:

A collections cache is stored at system/collections.json
The cache is read only, changes made to it are overwritten (it is regenerated)
on device disconnect

A log of collection creation/manipulation is available at
system/userannotationlog

collections.json refers to books via a SHA1 hash of the absolute path to the
book (prefix is /mnt/us on my Kindle). The SHA1 hash may or may not be prefixed
by some characters, use the last 40 characters.

Changing the metadata and resending the file doesn't seem to affect collections

Adding a book to a collection on the Kindle does not change the book file at all
(i.e. it is binary identical). Therefore collection information is not stored in
file metadata.