Ok, I played around with this stuff and made some preliminary configs for the new build system.
The main difference from the config in this thread is that instead of setting Y2_USE_ENDSTOP and Z2_USE_ENDSTOP these settings are removed. This will allow Marlin’s pins.h to do the right thing and automatically use the DIAG pins configuration it already has for the board.
I would appreciate if @KCGreg you could download one of the zips from my repository and see if it buillds & works for you. Below is a link to the latest build as of 07/22.