Would you be OK with an “Open with...” menu item to show the notes inside a more advanced text program? I don't feel like printing notes is something that fits right into a post-it application because of their small layouts.
This means 3 operations for printing (open folder, open in editor, print) instead of 2, but that would be OK since, for me, printing notes is not such a frequent action.
You should be able to open notes folder in Thunar through notes settings dialog -> Select notes path -> right click on the chosen folder -> Open in file manager.
After this you should be able to open notes files in any editor you wish.