If there are multiple Shippers Invoices on the same shipment, and the ABN/CCID is different for each Shipper against the Customs Entry, then it will print “MULTIPLE SUPPLIERS – REFER TO ENTRY LINES’ in the Supplier field.
It will also list each individual Supplier on the Import Declaration.
Please see screenshot highlighted below for your reference.
NOTE: As per current functionality, if there is only 1 Suppliers Invoice on the 1 shipment, then it will only print that Supplier Name.