I am not sure if there is a concept behind that some expressions can be converted to performance data and some others not.
Adding this for dynamics and hairpins should not be a technical problem as it's very basic to convert this to or pick it from the volume graph at the specified symbols bar locations.
I guess there could be also some extensions like:
- Tempo marks for numeric values, acc. or rit. could work similar to volume marks and hairpins
- Pitch bending symbols could be more delicate to apply or retrieve but I think it's not impossible too and it would be very helpful for guitar and synth bending - see Notion 3 to get an idea what's possible...
Maybe some is already on your list for a future update?
I don't think volume and tempo are too fancy for everyday musicians.
