I'm glad that you were able to solve the issue. Yes, aside from using
ApproveOrders action, you can also also use the
SubmitOrdersForApprovalAndOverbook action (on which you did) and
ApproveAndOverbookOrders to bypass the "Not enough inventory" error. You can check all the action methods of an order in this
document. In the document, some of the action methods are under the reference document of an action. An example would be the SubmitOrdersForApprovalAndOverbook action which is under the SubmitOrderForApproval action in the reference document.