Another thing one could try, albeit a little bit of a faff – plug the van in, run heating at maximum for 15 minutes (or thereabouts), and place a dehumidifier in the centre of the car for another 30 minutes or so (keep the heating running).
If this really is condensation, and i still doubt it, you need to increase the capacity for the air to carry moisture (= heating it), and then catch the moisture (by dehumidifying).
In general use, condensated water won’t go anywhere, it doesn’t disappear, it’ll stay in the car until spring/summer. The only way to get rid of it in winter is by actively dehumidifying it – either slowly through charcoal packs, or with a sledgehammer (=dehumidifyer).
Prior: SEAT Ateca Xcellence Lux 1.5 TSI DSG MY19, VW Golf GTE PHEV DSG MY23
Current: Hyundai Ioniq 6 Ultimate
Next: we'll see what's available in 2028.