Welcome to the Community. I can share what I know about the packing slip in QuickBooks Online.
The default setting in the system will depend on the subscription region. Some will show as Packing slip, others as a Delivery note.
For now, the option to change the display name is unavailable. As a workaround, I recommend downloading the packing slip and manually update the information from the PDF file (see screenshot below).
You can also search for a third-party application to help you edit the downloaded file from QuickBooks.