'Note Model Description Language' works for me!
I created a very simple notebook with 5 strokes: Pen, Fountain pen, Marker, Pencil, and Highlight using the blank page template. Except for variations in stroke weight, pressure, tilt I think these are the only entities you can create currently with Pen. The templates must have some others (shapes? text? lines?). I'll pick a few of those and post examples of those next.
I'm going to start reading up on SVG and Python libraries for that. It seems like the way to go as a conversion target.
https://github.com/amazon-ion/ion-python (Python library for Amazon ion)
And yes, interesting that NMDL is so low level.