Hello,
Those are really special keycodes you are looking for.
Please find below a list of all supported QMK keycodes:
https://docs.qmk.fm/keycodes
Maybe Props could be KC_CRSEL.
Also not all keycodes have a name mapped into VIA/VIAL, in this case there is a need to directly type the hexadecimal value.
This sucks but neither VIA or VIAL teams look to be willing to have complete keycode support in their application.
That was it exactly, thank you!
No glamour shots until I get the keycaps I forgot to order, but this is what the completed mapping looks like for anyone else who wants to pretend to have a sparcstation but with better keyboard: