I read on the Golf R forum that it’s the shortcut to the climate control screen. Have you tried tapping it when the ignition’s on? If you do, then it should load the air con screen.
From the Golf R Forum;
‘If the symbol or other air con related symbols are showing when the ignition is on and infotainment has loaded and is active, then you can access the full air con screen via them, but if it’s the air con symbol showing as the system is closing down at ignition off then I believe it’s just showing the status of air con at ignition off stage but, it will no longer function as a button once the ignition is off. The air con will be on next time you start the car.’