Starting point from the old fabia-vrs forum, this should confirm if it is actually possible.
Enable Cruise Control Using VAG-COM (VCDS)
Connect your OBDII lead to the car. Switch on the ignition and start VAG-COM (VCDS)
Carry out a full check for stored error codes, note and reset any that you find.
You will need to ensure that your Board Network Controller is suitable for Cruise Control. Open the controller 09 and ensure it is either 6Q0 or 6Q1 and not 6Q2.
Open controller 01, when it logs in you should, in the upper right corner, see either OOOOSG if cruise isn’t enabled or GOOOSG if cruise is enabled.
To enable cruise, choose option 11 Log In and enter the code 11463.
Close the controller, then open the controller again and confirm that GOOOSG is shown. You can also confirm by starting the car, stopping it and then scanning for codes on controller 01. You should have a fault code logged which reads something like cruise control system signal implausible. Clear the code and put your VAG-COM (VCDS) away.