In Cubase Pro 9.5.1, when using the chord assistant in a chord track, the complexity settings don’t matter when adding a new chord.
I choose mode Cadance, type Full (I-IV-V-I) and complexity 1.
The chord assistant than show all chords that match those criteria.
When adding a new chord, the chord assistant shows me all available chords for complexity 7, despite the complexity 1 carry over from previous chord. I have to click on the complexity once more for the changes to take place.