User defined cost does not work well and often causes issues.
Adding direct and indirect costs can be a nightmare. You create a non inventory item (one per type of cost), check it as being used in an assembly, enter the cost of a qty of one of that item, select the cost account you use to buy or pay for the item, and an income account.
When you issue the build command QB will look at the non inventory item and fetch the price you put in the cost block and remove that price from the expense account and add it to the assembly item.
See the problem? The cost must be updated and paid before you build the assembly item or the expense account can be driven negative (causing income on the P&L)
IMO doing any of that is more problems than it is worth. Payroll, labor expense, is already an expense, why remove it from the expense account and put it in an asset (the assembly). The same is usually true of all other indirect expenses.
Your choice
