Looking through Apple’s documentation, it does look like Duplex has some interface within their printing system: Apple Developer Documentation. What I cannot find is the method of accessing the printing presets. If we could just choose a preset, we could set up a preset with Tray 1 or Tray 2 and switch between them as necessary. It might be possible through the CUPS interface, but it has been a while since I fiddled with that.
It is frustrating that there are things that you know have to exist, but knowing how to find and access them is so difficult. I was talking to a neighbor in the coding business about how it seems that so much of modern programming is a few basic concepts and a big bag of magic tricks that you have to sift through to find what you want. At least Panorama has a Help system that tells you what is in the bag in one central place, although knowing which magic trick you want is still difficult.