Custon navigation tree help

[Chilledblue]

I'm trying to figure out how the custom navigation tree set-up is working, not the pictures and music node section, those are quite simple to understand, but the video one.
There is no documentation around and I've searched through this forum but I did not find any answer.
Are someone that can explain how it works, what is a level? For example how the keywords type works on the video node section.

Thanks in advance for any help.

[PeeBee]

There is offical guidance in a zip file attached to this sticky thread.

PB