Grouping 4 Asins into 1 variation family

Ok, I’m going slightly insane here.
I have 4 jar products (already listed on Amazon) that I want to group into the same variation family.
When I try to do it via “add product” button, it says that particular category doesn’t have variations. (which is not true, because other sellers have plenty of variation products in that category)

If I try the Spreadsheet Upload method, it gives me stupid mandatory fields that aren’t even relevant. Or variation themes that are not relevant.
I’ve literally been trying for weeks and customer support have been incredibly useless (probably because they can’t make sense of it either).

What do I do?
Is there a tutorial on how to combine several ASINs into 1 variation family I can watch?

This should be so simple - I don’t understand why Amazon made it so complicated… sigh

thank you for your help!