Hello @travis-mc
Shopify Shipping doesn’t support combining multiple packages into one label.
However, the Multi Carrier Shipping label app allows you to create Multi Piece Shipments (MPS).
The app automatically selects the right box based on weight, volume or maximum weight, offering rates at checkout and generating shipping labels using multiple boxes.
Keep in mind that for specific or complex packaging needs, approximate rates may be offered at checkout, and you might need to adjust package dimensions when generating the shipping label, as full automation may not be possible in such cases.