How can I sort my packing list by SKU without a third-party app?

I am trying to understand and ultimately change how my packing list is sorted.

I’ve been trying to read about this but i can’t figure out how it is sorted originaly?

Getting my packing list sorted by SKU would make things so much easier, but i dont want to install a 3rd party app just to change how the list is sorted, everything else is fine regarding fulfillment/shipping.

Anyone have any tips on where to look in the template?