There are two steps to doing this:
- Declare a marketing custom source for QR codes and apply a campaign to each QR code.
Tools > Sources and campaigns > Marketing campaigns > Custom > Sources: add a new Source for which you can add as many variables as needed. Please note that only variable C is required to declare the source. Here the source can be named "QR codes".
- Tag the link in the QR code.
The format should resemble the following: https://www.site.com#xtor=CS1-2