Not sure if anyone can help, I have found with the P6, as mentioned by @robotheart, that if you have the hold button engaged, provided you keep at least one key depressed, you can add notes to the arp, however if you let your hands off all the keys, you are not able to add notes to the sequence, as it basically retriggers based on the notes you press.
I have been watching this amazing performance by Hania Rani, she has a prophet08, however as you can see in this link, she is adding notes to the arpegiator sequence even though she has let her hands off the keyboard completely. Is this a different latching system built into the prophet 08, or can you achieve this with the prophet 6 also?
https://youtu.be/_3EuiU1qdpE?si=lB8pdzDnjZ5wi7qx&t=251 - i have timestamped but if it doesnt work you can see it clearly at 4:50
The only thing i can think of that might work, is sending a single held midi note to the prophet that correlates to the key you are in, and you should be able to continuously add to the arp (provided the hold button is pressed) without needing to constantly hold down a single key on the keyboard.
Any feedback would be great!
thanks