You've created a barcode, but now you want to make this as a variable for your end user to update the URL.
I've got my barcode added.
You can see under the barcode tab all of the settings
I'm going to go to the variable data tab to add a variable.
I am going to name this QR code, and then the type should be short text.
If I were to go back to my barcode, there's now a variable dropdown here
I am going to select the QR code and apply.
You'll notice that it is now saying that there's no input data.
If I were to go to my variables tab on the left under, under QR code, I could set what that variable should be knowing that my end user will change this once they get into Tempo.