Comment by mikeayles

This isn't using the KiCad socket API, although it probably would have been cleaner. It's a bog standard Plugin that should work for v6+.

I'd be keen to have a look at your s-expr library, it likely has some overlap and utility for one of my other projects, https://www.circuitsnips.com , which is like thingiverse for electrical circuits. I had to figure out how to feed the embedded kicanvas renderer a full sheet, as it can't handle subcircuits, but allow the user to export subcircuits to the clipboard.

When I first shared CircuitSnips with the KiCad discord, the KiCad 9+ design block feature was brought up, which might be of interest to you as well?