Weird, I had no issues adjusting mine. You said the engine was warm, but any chance it wasn't hot enough? Maybe go on a long drive first to get it nice and hot (if you didn't try that already). Also, did you try adjusting it while the engine is running? The idle would definitely change for me while adjusting up/down. Beyond that, I'm out of ideas!
To echo what everyone else says: if anyone legitimately knows of a way to adjust idle by more than 50 RPM with OBD11 or VCDS
and posts the coding, that would be outstanding! Not holding my breath though