Hmm I’m playing around with the Logical Editor and I think I see the issue. So, you can actually select all the root notes for a set of chords automatically.
Context Variable->Equal->Position In Chord->Root
However, inside the “Position In Chord” function, there is no way to select “highest note”. There IS a highest note option in the context variables, but it will only select the highest note of the entire midi part, it won’t calculate it based on the individual chords. Also, there is an option inside the “Position In Chord” for selecting specific intervals from the root (maj 3rd, perfect 5th, etc…), but there aren’t more relative options like “2nd note from the bottom” where it would select the note 2nd from the bottom regardless of what interval that may be. In fact, there isn’t an option for selecting the low note either, just the root, which is often not the same thing when dealing with inversions.
So, Cubase actually does already have a system/algorithm in place for detecting all the chords in a MIDI part. They just need to implement more commands/functions on top of that. Inside of “Position In Chord”, there should be a “Top”, a “Bottom”, and perhaps other options like “2nd from bottom” or “2nd from top” etc…