Pro-forma Invoice After Payment


I am trying to use a pro-forma invoice as a customs invoice to ship final goods. I am using Odoo version 14. The pro-forma option seems to disappear after I create an invoice on a sales order. My workflow is:

- Send a quotation to a customer for confirmation
- Send an invoice for 50% down
- Manufacture goods after payment received
- Adjust Sales Order for actual deliver quantity, add freight and other additional charges
- Send a final invoice deducting down payment
- Generate a commercial invoice that only shows value of goods, no down payment, for customs purposes

I am struggling to find a way within Odoo (no third party apps) to generate a shipping invoice. This must be a common need! I was hoping I could format a pro-forma invoice to fit my needs, but the option is gone after I create an invoice and request payment on the SO.