This Calibre plugin allows you to manage your Kindle collections, and, on select devices, margins and fonts.

Main Features
Works on the Kindle DX, 2, 3, and 4 non-touch; and in tandem with ixtab's Collections Manager on JailBroken Kindle Touch, PaperWhite, PaperWhite 2, Basic, Voyage, PaperWhite 3, Oasis, Basic 2, Oasis 2, PaperWhite 4 & Basic 3 devices