How to add non-stock item for COGS on Sales Order

Summary:

Customer wants to add non-stock item to the sales order such as Labor and sometimes material (parts) and collect cost on them.

These items should be collected for Costing but depending on how item was sold (Transaction Line Type Code) it may be invoiced or may not be invoiced.

The cost should be recognized when order is invoiced.

Is there any orchestration, workaround or another solution that can be used for non-stock item to handle these two scenarios?

• Non stock-item - COST but do not invoice
  When service is sold as a pre-paid product, the labor and parts are used but the customer cannot be charged for it. However, there is cost involved so line should be collected in costing.