Once you’ve identified all the units of inventory to bill out, use the ‘Invoice Transfers’ utility to create the A/R invoices. Navigate to [i] Inventory, then [e] Invoice Transfers.

The uninvoiced transfers are listed:

[I] Inventory | [e] Invoice Transfers.

You can select any number of transfers to invoice. Once created, the invoice item is populated and is a hotlink to the new invoice.