Tell me where to look (maybe there are ready-made solutions?)
There is an attribute "Size" which is used in creating variations. Must add European size and American.
But if we add these two sizes, then the variation is formed from two of them and in the product card you need to select both the first and second sizes, although this is the same product.
If the second size does not participate in the formation of the variation, then it is not attached to the values of the variation and goes to the entire product card.
Through additional fields for variation … perhaps, but not convenient and not beautiful. A lot of work with other extensions … avalanche.
Perhaps a certain mapping / replacement table?