The buttons do what they did since the early versions of BIAB.
You will see the whole chord, if the notes of the chord are played at the same time.
If the chord is played as an arpeggio, or one or more notes with a little offset, the button will scroll through the timeline and visualises the notes played at the same time.
If you open the leadsheet and guitar window you can see exactly what happens.


Norbert
------------
MacBook Pro M3 Max / BIAB 2026 Cubase 15 / Reaper