I have a store wich sells personalised products with portraits. When the portrait is ready you are send to a page on my store where you can review your art and approve it. I want to place some upsells on that page for 1. a sticker of the portrait and 2. the digital file. It should be that when you click "Get your file/sticker" you are redirected to checkout with the product in cart so there is a higher conversion and less friction.
How can I custom code those dynamic checkout buttons on a page in shopify?