Happy New Year Yang. While I don't have a Nallo 2, I have another Hilleberg, the Allak, and I imagine the inner and fly ventilation mechanisms are the same.
I've had great experience snow camping with it with two people without condensation issues just by unzipping a few inches of the outer fly door at the highest point under the cap that sits over the tent poles and fly. The fabric inner door under that is breathable.
If you need even more ventilation, you can unzip the fly door a little more, and you can also open up the inner door zip at the apex of the door.
I've found it very easy to minimize condensation, while keeping out drafts and keeping warmth in.