Unfortunately CNCjs is light on shortcuts, you can check all those implemented in this source code file
You could either modify CNCjs and rebuild it (did it once, not terribly complicated but not easy either), or use the pendant approach and then you can send the Gcode you want to the machine, including zeroing commands, but that bypasses CNCjs so not great to ensure consistency with the GUI state
CM shortcuts are here (they may have changed in recent builds, not sure)