You can set up randomized step sequences over select parameters in many ModFactor algorithms, by using Sample & Hold modulation:

https://www.eventideaudio.com/community/forum/stompboxes/some-random-h9-presets

But in my opinion, plugging in something like the EHX 8 Step Program to the expression pedal input is the ultimate in control.

Yes, it’s an external device, and adds $125-150 US to the cost.  Between the extensive capabilities of the ‘Factor / H9 pedals, and the deep programmability of an external step sequencer, it’s like designing your own pedal (or creating your own algorithms).