With. It’s not realtime but you can record your arp chords, play the track and record notes on another track.
With external keyboard, Arp is active only if the track is active. So I think it wouldn’t be possible to play a track with arp while recording notes on another track.
Why do you want to record notes independently from arp ? You can record arp notes of the Beat Step Pro in the OT…
Are you sure Beat Step Pro records only notes ?
I watched the video, but nothing confirmed it to me.