We have AP invoice approval enabled for non-PO invoices. We have a PO matched invoices for which the

We have AP invoice approval enabled for non-PO invoices. We have a PO matched invoices for which the Approval status changed to "not Required" after the workflow process is run. User is adding Mnual lines to this invoice and the Manual lines are going to Approval not required status by default? we are expecting approval process should start again as new lines are added to this invoice? please confirm if this is intended functionality or if there is a solution for this?