I like the idea of connecting a USB MIDI controller to the E1 and using it to control the E1 itself.
For example, I could press keys on a Korg Nanokey to switch pages or presets on the E1.
Or how about just turning a knob on a Behringer X-Touch Mini to indirectly control one of the E1 knobs? That would make it possible to leverage the power/flexibility of the E1 on lesser/basic MIDI controllers that can typically only handle CC’s but not complex RPN/NRPN/sysex messages (eg. set an E1 knob to use complex sysex, but let an external MIDI controller adjust the E1 knob via a simple CC). Lol, controlling a MIDI controller with another MIDI controller!
I saw some mention of external MIDI controls in the docs, but don’t see anything like a MIDI implementation chart for the E1, so I’m not sure how to proceed.