Great question.
Channel Changer
Changes the channel for the subcontrols.
In addition, it saves the value for each of the subcontrols per channel. When the Channel Changer supercontrol returns to a particular channel, the subcontrols snap to their previous values.
Channel Changer II
Changes the channel for the subcontrols.
Let me know if you need additional clarification. You should have three MIDI Designers on your iOS device at all times, at least: Pro, Lite, and 12. That way you can experiment freely in one and check stuff out without messing up your layout. Also, though, mailing your layout to yourself is bullet-proof.