I don’t think this can be done from within Thunkable using the existing components. But you could definitely use an API to create the QR codes and retrieve them in the app or in a data source that the app has access to.
To make the QR codes unique, I would use the Firebase Sign Up/Sign In blocks in Thunkable which generates a unique user ID. And then I would send that to the QR code generator either as is or with extra characters (e.g. MyAppName_UID_34591023459).
In fact, here’s that same text as a QR Code I generated with the url https://api.qrserver.com/v1/create-qr-code/?size=150x150&data=MyAppName_UID_34591023459 using the free QR Code generator at https://goqr.me/api:
