How to generate costs for Bill Only Sales Order?

We currently handle some business where we issue invoices on behalf of others, but we do not engage in any production activities and therefore have no inventory.

Therefore, we plan to enable the bill-only sales order type to support this business flow. However, since there is no picking operation, we cannot generate cost of goods sold and will only generate revenue.

We want to use the bill-only order type while still generating the corresponding costs. How can this be achieved?

I have already raise a SR for help, but

Order Management does not support this out of the box, as there is no direct integration that bypasses the inventory interface.