Yes, I agree it would be a game changer if those sequences of the Harpeggiator were editable. It is possible to implement it software-wise but there are two main problems:

1. It will take a lot of time to rewrite/create new modules in the code of Harpeggiator algorithm.

2. It would be impossible for users to create custom sequences on their H9 or PitchFactor without H9 Control.

Playing devil’s advocate here:

1.  Still non-trivial, but how about commandeering the last available ‘slot’ as a programmable sequence?  For pitch, say, #26, in Sequence A / B [as I assume the Random values are mathematically generated].

Of course, this is going to lead to a programmable Rhythm A / B pattern FR [in, for example, Slot #20].  The default pattern(s) would load as the original fixed pattern, as to not break backward compatibility.

2.  MIDI Note input (unused in the rest of the PF / H9 implementation).  For pitch, maybe a two-measure MIDI Note sequence, center on middle C for Unison input, with a one-octave spread on either side.  It could be ‘loaded’ by an external sequencer / DAW, MIDI controller / keyboard, or even MIDI pedalboard switches.

A similar setup for programmable Rhythm patterns; perhaps using the extreme low end (or high side) MIDI Notes to determine relative ‘groove’ levels for the 16 sequence steps.  Just a thought.