The Tracking number should be saved in the order 'shipping' section and in the ticket fields to the left in Zendesk. Adding the ticket# to the 'order comments' also helps to cross reference orders with tickets.
Reference Codes -
PWR - Product Warranty Replacement
PWC - Product Warranty Cost
PFS - Product w/ free shipping
PSC - Product plus shipping cost
M - Miscellaneous
On the UPS Label itself there are 2 Reference lines and should be filed using the following format -
Reference #1 = Order # Ticket #
Reference #2 = Applicable UPS code from above
When creating a return label, be sure to select the 'Options' tab and then change the 'Return Service' option for 'Shipment Return Services' from '3 UPS Pickup Attempts' to 'UPS Print Return Label' and be sure to copy the info from Reference #2 into the 'Merchandise Desc for Package' field.