I think it would make sense to keep the adjustment section disabled/hidden/no...

I think it would make sense to keep the adjustment section disabled/hidden/not-present initially.

When an order item is added, then the adjustment will be available. When an adjustment type is selected, we provide the option to select one of the order item, and we make it mandatory. I think this is how we would be able to associate an adjustment with order item.

I will try to compose an init code.