OK that was quick!
I loaded WB 1.3 and opened HDInstTools. I went to DH2: and edited the partition. The drive was not set to bootable. I quickly changed that. I also changed the boot priority to load last, but that setting did not take. I think I need to delete the partition and rebuild it for that setting to take effect.
But as it stands right now, I don't think it even matters. Simply making the drive bootable appears to be all I need for the Amiga to see it during launch. Behold when I flip my KS switch and boot 2.04, with 2 mouse buttons pressed:
And after selecting DH2 from the boot menu, it goes directly to that partition which I've allocated 22MB for WB 2.04 "stuff". I am so STOKED! I can finally finish some of these other projects I had to put on hold until I had a nice comfortable 2.0 solution without jumping through hoops.
I will try the startup sequence approach one last time. But if it doesn't work? I don't care so much anymore. Pressing two mouse buttons down to pick a drive to launch seems pretty elegant on its own, and realistically only adds a couple seconds to my boot-up now. Big friggin' deal!
But I will try the SS one more time, as that would be epic if it worked.