If I want to "add a card" to a product that only has a quantity of 1 to start, it makes a new sku and if they choose the card as an add on, it doesn't deplete the inventory on the original art.
I ended up adding it as a form after clicking "buy now" and giving it for free but I want to charge for this add-on in the future and can't do it in the form.
https://www.letsresin8art.com/shop/p/heart-magnet-b2a26-2sgww-25thn