🇩🇪Germany @swms

And unfortunately, on the project we were using a custom checkout system: users would submit a node form and the product would be configured and placed into the cart automatically. So it was all custom code. I do have the relevant code for creating an order item and putting it in the cart, I'll dig it out when I have more time

Has this "custom code" been published somewhere?

I am looking for a similar solution (like in Commerce Node Checkout) where a user creates a node. On the node form there are several options (pay to publish, pay to promote to top of lists, pay to promote to front page, ...). If one of the options is marked, after saving the node, the user is redirected to the shopping cart, pays and the node is published, promoted, ...