UPDATE: SUCCESS. After a lot of work tweaking config files and compiling firmware, I finally got Sensorless Dual Homing working for both Y and Z on my LowRider v2 with SKR Pro 1.2 and TMC2209 drivers! 
I feel like I became a junior expert on this. LOL.
Details on my efforts (and a download of my build files, configs, etc) are available here: Doug Joseph (Design8Studio) Full-Sheet LowRider 2 "Build on a Budget" - #11 by DougJoseph