Wanted to report a discovery I made today in case it might help other sigmarion 3 owners in the future!
If you look in the registry at:
HKLM->Software->NEC->Touch Panel
There are registry keys F1-F10. These allow you to override the shortcuts for all the HW shortcut buttons around the screen.
Why does that matter? Because from the control panel you can only override F1-F5 aka the buttons on the right hand side of the screen, not F6-F10 aka the buttons on the left hand side!
Now I can launch total commander from the mopera button, the control panel from the mobile custom button, tcpmp from the Windows Media button, and npop uk from the Windows Mail button! Sweet!