Generating arpeggiated chords in plug-in - dox for

I have been tweaking the "Expand Chord Symbols" plug-in by Mark Shepherd. I am now trying to have the generated chords be arpeggiated. A look at a .mscx file shows that I need to have an tag added to the . has a integer that specifies the type of arpeggio.

Mark's code builds chords from an array of MIDI notes. This works fine.

                    cursor.addNote(midiNotes[0]);
                    if (!chord.bassOnly) {
                        for (var j = 1; j < midiNotes.length; j += 1) {
                            cursor.addNote(midiNotes[j], true);
                        }
                    }

I searched the dox for an arpeggio object, but found only Element.ARPEGGIO. I can use newElement(Element.ARPEGGIO) to create an object, but where can I find document on that properties and methods the object has? Element has a "subtype", so I tried adding this after the note loop:

                        // Arpeggiate the chord
                        var e = newElement(Element.ARPEGGIO);
                        e.subtype = 0;
                        cursor.add(e);

But it doesn't affect the score as viewed or saved.

Mark's code builds the chord using Cursor's addNote with a "true" second parameter. I PRESUME that Cursor wraps the notes in a Chord object. So perhaps my Arpeggio is ending up outside the Chord object.

I thought of newElementing a Chord, and populating it with Notes and my Arpeggio. But both Chord and Note have a number of parameters, which Cursor.addNote take care of and whose initialization isn't clear to me from the dox. Is there some other way of making "easy" Note and Chord objects as Cursor.addNote does?

Or is there a way to ask Cursor for the Chord that it presumably has created?