Volkswagen has actually managed to design the on/off knob of the infotainment system in the worst possible way. Instead of only turning the ring of the knob, the whole switch rotates together with the label.
When the symbol wasn’t straight, it made me incredibly nervous.
It is practically impossible to adjust the volume to a tolerable level without the symbol being at an angle. WTF Volkswagen?!
Vinyl stickers to stick on!
There are two ways to stick on the knob. Either you just stick on over the inner black part or the complete knob and loose the switch illumination.
Only the inner part is (badly) sticked over 
The complete knob is sticked over
I had a lot of problems just sticking over the inner area without the sticker sitting crooked, which is almost as bad as the crooked print.
My solution is to stick the complete knob with the renouncement of the instrument lighting. But I can live with that.
+5 to satisfaction
Technical Data and Howto
In Inkscape I drew a circle, dimensioned it with the respective diameters and cut it out on matte-black vinyl in a laser cutter.
The small sticker for the inner part: Diameter: 11.88 mm
The large sticker for the complete rotary knob: Diameter: 14,62 mm
Clean the knob well, stick it and you’re done.
Update: 10.03.2019
Due to the many requests, you can now buy the large stickers here: Link