I would suggest to take a look to the Simphony SIM Script User Guide
Read the "ISL Printing" chapter and also the "Event...EndEvent" to catch the event used to print out something.
In order to print QR code you'll have to struggle with the ESC/POS character format and the specific printer protocol.
The .Net extensibility is much more flexible and would give you more tools to handle the print out, but it's more tricky to use, since the documentation is limited to the one published at the following link: https://docs.oracle.com/cd/E91245_01/index.html
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