Ah, I see. Yes, I was missing the key point – you’re dealing with the built-in store. I don’t have any good ideas. Sorry.
Javin, if you didn’t come across it already in your search for a solution, you might find this interesting: https://support.wix.com/en/article/velo-tutorial-adding-a-related-products-area-to-a-wix-store-product-page
I realize that it’s not a solution for you – it requires that connections between individual products be made manually – but it does bring ‘related’ products onto the product page. I haven’t used it. I stumbled onto it just now as I was looking for possible answers, and I thought you might want to see it.
Good luck!