Moving from Note Air2+ to Air 3C - where's the Dark Mode????

I'm dismayed. I've waited for ages for Neoreader to have a dark mode, and it's fab. But I wanted to move to an Air 3C, which is meant to be superior, right? Wrong!  On the Air 2+ there are different options for adjustment - You go "Style" and there's one called Margin. In Style->Other, you go into that and on the background options there, you can select Original, white or DARK.   There is it!

In the Air 3C, there is no Margins tab, Style is called Format, and and in Format -> Others, there is no Background options row, and no Dark settings.

Does the Air 3C have that???  Why not? Help!?!?