I did a series of experiments, and the big pad at the bottom was always the previous chord in the chord progression. Which makes sense because it’s trying to suggest where to go next in your progression.
Still no idea about the “ Right-click the chord pad that you want to use as a starting point and activate Use X as Origin for Chord Assistant ” Right-clicking on a pad does nothing in my version of Pro 11 but back in version 9 there was a report of some problems in this area: A Chord Pad Bug after update to v9.0.20
What do other people here get when they right-click on a pad in that tool?