Do you want to edit the SONAR MIDI track that drove EZD1?
If so you do that the same way you did back in the EZD1 days. Open PRV, etc.
Now if you mean you want to take your MIDI track in import it into the Song Arranger of EZD2, I honestly do not know how. I've interpreted statements to the effect that you can.
Hopefully Mod Bod will be along to describe that process.