While debugging our BASIC on MKRzero style boards, I was able to brick a couple of them before figuring out all the proper procedures. So to fix that the stock MKRzero needed a pogo pin (spring loaded) connection to a JTAG connection.
So just got back my 2nd KiCAD project. This one was quite simple compared to the microBGA design that was my first. It was also the first one that was built by OSHpark, and that translation was much easier than what I use to have to do with Traxmaker.
Quite impressed with KiCAD. Here is a the whole board, laid out to handle MKRzero, Protoneer Nano, and uChip.
Details at the forum