It would be very helpful for an API of some sort to be exposed, so developers could make various plugins.
A few ideas:
- Programmable notes (Useful for maths - insert difficult sigma sums, calculations etc)
- Ability to tap into handwriting recognition (recognise chemicals, equations, etc)
- Siri/ shortcut support
- Custom shape snapping
- Themes

I'm sure there are more things developers could do with this ability. Take VSCode for instance. Granted it was built from the beginning to be easily modified, but their plugin ecosystem is incredible.