Thanks @jomaxro ,
I did create parent-child relationships, but still this doesn’t work for me.
Quote myself:
" If someone chooses ‘Audi’ as brand, then the tag ‘Audi-models’ should be mandetory. If he chooses ‘Volkswagen’ as brand, then the tag ‘Volkswagen-models’ should be mandetory."
As far as I can see this is not possible. I can make Brand mandetory en set the minimum of tags required to 2. In that case the first tag they can only choose a Brand, because that’s the parent. As the second tag they can choose an Audi model, but also another brand! So they can choose two brands instead of the mandetory Brand+Model
Is there a way to solve this?