I have added the magnetic connector (sort of)--I have put three vias on the PCVB routed to 5v, a GPIO pin, and ground. This way I can use a ribbon cable to connect the sigil LED to the magnetic connector. That should be sufficiently secure inside the device, but allow the top of the shell to be removed without risk of damage. I also plan to have the case only held together by magnets--no screws on the outside. I was also able to make the knobs bigger.

I ordered several parts from Adafruit (although I forgot the @$#%& magnetic connector. Hopefully other things will be needed to share the shipping cost.

In the process of doing this, I realized that I don't need the stepper chip at all. I can get 5v from the Pico, so don't need to step up 3.3v to 5 for the LEDs. So I'll pull that thing out.

I'm also trying to figure out how to get JCLPCB to put one type of component on the board, but not the others. I think I have it figured out, but that's a challenge for another day.