Has anyone determined where the customizable function choice for the Mavic Air Camera Forward/ Down is?   
Is it missing ?

Nope you have the camera scroll button the left side of remote to move it

It does not appear to be available on the Air as a custom setting.

Isn’t that rather unusual?   Don’t most of the Phantom, Mavic Pro and Spark have that functionality?
Is this something that can be later added via firmware!?

I was very surprised to see such a popular functionality disappear.   DJI??

I miss having it :-(

Yeah, had a Spark with this setting and it’s invaluable. DJI better add this in a future update.

Yea it has to be an oversight, clearly it could be easily added to the Fn button or an onscreen button.  DJI can we get a stance on this?

If I were DJI, I would save that feature for Mavic Air 2 Pro Platinum Obsidian edition.
But luckily, I am not.

You should be able to set C1 or C2 for that.

I believe that G-Sig is mistaken about C1 C2, that does NOT exist on the Mavic Air RC, that's what we were discussing, not the Mavic Pro.