The main lesson I learned was probably to start thinking "in hardware" and not software. Like you design something and it fits on paper but in reality, it might not be ideal. For example, my diode placement is very close to the hotswapsocket (i fixed that for rev 1.1). On paper it war fitting, but its kinda hard to solder when you need room for your solder iron in between - this is something kicad won't tell you.
Thanks. I must admit I am curious to see what mistakes I’ve made this coming weekend. My first KiCAD PCBs should arrive this week, then the penny shall drop I suspect.
If you’ve not tried it yet I’d recommend having a go at reflow soldering with a hot plate. It makes some aspects of assembly easier.
I haven’t yet had a chance to get two rotary encoders working under ZMK yet either. Did you have a good resource to use for that or did you need to figure it out yourself?
There is a zmk pull request open that adds split encoder support. If you use that to build your firmware if should work.
To be honest I have not tried it with this board so technically one scrollwheel is not working right now. Though I'll change that soon. I used a fork that supports split encoder with zmk on my sofle and it worked, so you could use this config for some inspiration (here: https://github.com/dnlbauer/sofle-zmk-config).