You can still change order status to “Refunded” on the web. And select “Finalize/Invoice” (convert to invoice) in WooPOS web order screen, and then create an extra manual adjustment invoice in WooPOS.
The outstanding web order items stock is “on-hold” in WooPOS. If you invoiced out or canceled/refunded the order, it will not be “on-hold” anymore. The final QOH = Received(PO) – Sold(Invoiced) –