This isn't really a product question, but regardless. Supermodes confused me. I searched and found @smitchmor's explanation, but it took me a while to figure out what his point was. I simplified it, elaborated it a bit, and posted it on my blog.
Here it is! If I've made any mistakes, please do correct me.
Thanks for the cool write up. We don't usually advertise this feature on the main site or in the manual since it's more of a by-product of dealing with borrowed chords and keys changes that happens to show up rather than something we thought people would use. Love to see the analysis you and others have done to explain the theory more fully to folks.