You don't. There are the 26 preset patterns, plus the random pattern sequencing. That's not to say that you can't 'edit' the patterns using the 'groove' and 'effects' sections, but those kind of tactics only selectively allow the preset pitches of a given pitch sequence through.
So the question of I can actually use the pedal in a real function band situation depends on whether I can find the sounds in the existing presets? Hmmm.
There has been a few posts here calling for a 'user-defined' pattern, or non-specific 'more patterns'. It's difficult to say how that could be implemented. Maybe a single, user-definable pattern, and external editing with a more sophisticated patch librarian. Or a direct upload to the device via a Standard MIDI File.
If it can be done externally, seems reasonable to me if a user interface is available.
Do you use MIDI in your bass rig? I've been using DAW and hardware sequencers (as well as LFOs and other MIDI controller sources, with upper + lower limits) to emulate HarPeggiator patterns. They target pitch-shifting algorithms other than the HarPeggiator, because the 'patterns' are all generated externally.
I have a Lexicon MPXG2 as my main controller and use some aspects of MIDI in patches, eg. using LFOs to control sweep filters. I use the tap tempo function in some patches too, but I would probably end up connecting the pitchfactor to the MPXG2 and using the tap from one to control the other.
I also have an Axon AX100 pitch to MIDI convertor that plugs into a Roland JV1080X but I only got that because I couldn't find a replacement for my Akai Deep Impact pedal. I don't use the MIDI rig live at the moment.
If you're interested (and you utilize the MIDI jacks in your system), I can go into more detail about the process.
Cheers, I'd appreciate that.