Nip wroteCan you select individual bars in editor and have them pop up on chord track or similar?

I duplicated track, and split into parts - then I can drag that onto chord track.

But what makes it stop?

If I understand your question, are you asking what makes the chord track stop picking up the chords you drag into the chord track? Maybe the track you are splitting up and dragging to the chord track doesn't haven't a bass note or is just simply detecting less that 3 notes.