Any reason why a custom field in the Inbound Shipment cannot be globally searched? It is created through Other Record Field and there's no option to mark it as something that can be globally searched similar to a transaction body field. Is this a standard behavior? How can you search for inbound shipment through the Global Search Bar?

inbound shipments are not globally searchable. Sucks. As for over-receiving, check out https://blog.prolecto.com/2020/07/18/overcome-netsuites-inbound-shipment-over-receipt-challenge/