This is a categories.xml file for the Nexus Mod Manager that has all the categories for Witcher 3.  I couldn't find a way to add them through the GUI (I could have overlooked it) so I used RegEx and made my own.  It uses the proper category ID for all of the categories on the site as of the upload date.  Version scheme will follow the Nexus Mod Manager version number.

FIRST, open Nexus Mod Manager, click the down arrow next to the categories button on the left, and select reset to Nexus site defaults.  This will make all the mods go into their correct categories.  Then, just extract the archive to your Nexus "mods\categories\" folder (backup old one) and overwrite, commonly found at "C:\Games\Nexus Mod Manager\Witcher3\Mods\categories". Check the images if you have questions.




NOTE: This file is unofficial and not supported at all by nexusmods.com.  I created this using a regex command from the categories page source.