[Nedorus]

First, thank you so much for the long and thorough reply. Greatly appreciated.
However it's not what I had hoped to hear 

I use kodi to play music videos and totally dont care about playing music on it as I have a Sonos system for that anyway.

So, filter type nodes don't carry over what I have selected to child nodes, right?

So that leaves me with folder type nodes, right? You said:

Most of the default (fundamental) nodes are folder type, they carry any options to the next level in navigation.

So how would I write a filter for just two levels, let's say genre->year

xml:
<?xml version="1.0" encoding="UTF-8" standalone="yes" ?>

<node order="0" type="folder">

    <label>Genres</label>

    <content>musicvideos</content>

    <match>all</match>

    <icon>some_icon.png</icon>

    <group>genres</group>

</node>

So this should give me the music videos grouped by genre, no?

I've tried several methods to create a "folder"-type node but they are always empty. I tried following this wiki instruction but with no success...