I can honestly say I don't think I've ever had an occasion to refer to either of these things. I rarely use them, because once I get them set I never move them. Since I'm the one who has to adjust them to my preference, I guess I've never had the need to refer to them - I just reach over and adjust them without speaking about it.
I've probably used the phrase 'adjust the vents', but even then don't think I've ever needed to refer to the parts.
I had had to use a term, I guess I'd call the one in the middle a knob and the thing on the right a wheel or switch.
Again, I've opened and closed vents with it, but don't think I've every actually specifically mentioned the item.