I think the Service Tag edit/change instructions are for some Inspiron models, like the Inspiron 14Z 5423 as it has a string in the BIOS similar to the one on the description page that starts with "$TAG" or hex 24 54 41 47. The UEFI Latitudes BIOSes don't have a sting like that and store the tag differently. I was hoping it would work on the Latitudes, but no luck. Still searching for a way...