Creating a backorder in odoo after you validate a purchase shipment isn’t as simple as you’d expect. Once you validate the delivery order, it’s marked as shipped. But, hey, there's a workaround for this!

First, you’ll wanna adjust the original purchase order to create the need for a backorder. Open the purchase order and click "edit." You can increase teh quantities for items where you got less than you ordered or add new lines for the extra quantities you now need.

By doing this, odoo takes into account this new demand in your inventory operations. It’s also a good idea to check your routes adn replenishment rules just to make sure they fit perfectly with your new order, especially if you’re using automated procurement.

Odoo’s whole supply and demand logic can be tricky. I had to tweak this once, so I know it’s not always intuitive. But when you understand it, you can manage discrepancies between ordered adn received quantities more smoothly, leading to fewer headaches and better operations.