What really surprises me is the fact that it seems you cannot "link" actual live products (including stock, descriptions, images etc) as variants? We sell luggage. For this example we have a collection named Fab Seventies which contains 5 different colors and 3 different sizes.
Is it correct that it is not possible to for example go the first product named above, make a variant of this smaller suitcase in size (medium, large) and actually select the second size as an actual SKU/product that is live in Shopify? So that all inventory etc is linked to this live product? That would make things so much easier..