I'm a beginner with this program, and this seems like the most basic question possible, but how do you add chords to a song?

The editor seems to only allow triads. How do you specify 7th chords, minor chords, flat 9s and all that? On the demo "how to enter a song in 3 minutes", it's hard to tell what the user is doing, but it appears to be keystrokes. Is there a reference sheet for what keystrokes go with what chords?

Is there a GUI where you pick chord, then the quality/extension/bass note/suffix?

This is for Mac OS X.