Hello,
I have a little problem. I use two libraries in calibre. When I use the plugin in the second library, I see the next error message:
The plugin try delete this collections because there are 0 books in the new library, but de Kinddle collection is not empty!!!, there are books for this collection in the first library.
And yes, I marked the checkbox "preserve kindle collections", but if the name in the kindle and the second library is equal, the plugin assign it to calibre, not kindle-only. This is correct.
And if I fill with 0 in the "minimum" field, then a lot of empty collections of the second library appear.
Non empty Collections in kindle are detected correctly, but the comparison is with Calibre, not with kindle... it's an error?¿
Possible Solution: I suggest create a checkbox in "Customize collections to create from Calibre"-> "Don't delete non-empty kindle collections. "
Sorry for my english, it's not my native language.

in advanced.