Carrier labels - Stock Batch Picking (link)

This module extends batch transfers (stock.picking.batch) with a delivery carrier and carrier options, so you can handle shipping for many transfers in one go instead of one by one.

On the batch form you get a new "Carrier Info" tab with the carrier, the available options, and a "Set Options" button. A warning states that setting options replaces the options already present on the delivery orders. When you pick a carrier, the mandatory and default options are filled in automatically, and you cannot remove a mandatory option. Changing the carrier on a batch also clears old tracking references on its packages and transfers.

From the batch list you can run "Apply a carrier and its options" to set the same carrier and options on several batches at once; batches already done are skipped.

"Generate Carrier Labels" (available to stock managers) opens a wizard where you choose the batches and whether to generate new labels even if packages already have one. It checks that every transfer in the batch has packages, generates missing labels, and merges the results into one attachment per batch, in PDF or ZPL2 format. The number of parallel workers can be set with the shipping_label.num_workers system parameter.