I have installed and configured plugin as
http://swiatczytnikow.pl/kindle-coll...omocy-calibre/ So I have used "Create collections on Kindle from calibre", restart Kindle etc.
Plugin correctly gets a collection of books assigned a "hand" in Kindle (communication : Kindle->Calibre is OK).
Books with collection assigned in Calibre after sending to Kindle in Kindle are "without collection" (communication : Calibre->Kindle is INVALID).