When the Sales Order is in Pending Approval status, checking the “Create WO” checkbox from UE script triggers NetSuite’s native logic, and the corresponding Work Orders are created automatically upon approval. However, once the Sales Order is already approved (and in Billed or Pending Billing status), if we add new line items and check the “Create WO” checkbox from UE script, the checkbox gets selected but the Work Order creation process does not trigger automatically. We need a way to retrigger the native Work Order creation logic for the newly added Sales Order lines (after approval), so that checking the “Create WO” checkbox again will automatically generate the corresponding Work Orders even when the Sales Order is already approved.

You need to test in UI first, if adding items to an already approved order, and checking that box, creates a Work order. If it does, then go ahead and spend time in scripting this use case, or debugging it. But if doesn’t, that means netsuite is natively not supporting the work orders on updated approved orders. Worth a support case in this case.

Adding lines to a billed SO can't be gaap compliant. If you have already recognized the revenue or the period has closed wouldn't this cause all kinds of problems. It seems like you have a process issue not a functionality issue