There are many ways to go with the EHX 8 Step Program covering the EXP PED parameters.  I'll confine the discussion here to what can be done with PLY-START automation.  We'll leave out Preset changes, Preset Cues, and omit the extensive MIDI control available (for virtually every 8 Step Program parameter). More information here.

Part 3 – Automated PLY-START via Expression

Tempo Control – Control the speed of the PLY-START position changes with MIDI Sync and Tap Divide, or asynchronous with the Rate slider, Tap, Tap Divide, or 'pass-through' Expression Pedal.

MODES (preset operations)

Depth – Normally set to 5 for Eventide pedals, but that value can be proportionally trimmed back with the 'pass-through' Expression Pedal.  Depth over 5 effectively brings up all slider positions towards maximum.

Glide – The time is takes to go from one PLY-START position to the next.  The range is 0-9; from an instant jump to slewing through all values between one PLY-START position and the next (slider).

Direction – Forward, Reverse, Bounce (Up and Down; inclusive or exclusive), and Random PLY-START locations.  This (and other) parameters interact with most other current Play Mode and Mode values.

Sequence Length – Active sliders 1-8.  It can be useful to limit the number of PLY-START positions, and control the locations with virtual LFOs [square, triangle, sine, ramp, sawtooth].

PLAY MODES (triggered by Play switch)

Loop – The 'normal' mode for sequencing through the sliders, then repeating.  The actual results are highly dependent on the current Sequence Length, Direction, and related parameter values.

1 Shot –  Plays the sequence straight through once, with no loopback.  This is great for a burst of PLY-START positions that returns to the starting point.

Step Thru – Each press of the Play switch shifts to the next PLY-START position.  Control over the 'grain' sequencing by foot switch.  It will return to the initial point and step through the current sequence again.

I'm sure that I missed a few items.  One note for MIDI users:  The 8 Step Program responds to MIDI Sync, plus Start (Continue) / Stop commands, which mirrors the H9 / TimeFactor Looper implementation.  It's a perfectly synchronized pairing.  For a little more info on Looper MIDI control (that I really need to update), check out this thread.