product and shipping - only one gets added, the other can be added manually - the frustration is that they wont' both add with the permalink

That does not work either.  I'm using a shipping and product discount, and that code doesn't work to add both to the cart, again only one will be added.  I changed it to exactly as you outlined (but with my codes, obviously)

I, too, am having this issue - can't amend the permalink no matter how hard I try.  The guidelines in the shopify dev docs here - https://shopify.dev/docs/apps/channels/cart-permalinks/cart-permalinks#step-4-apply-discounts-optional - specify you jus...