/bind numpad4 "say Engaging"The foundation of every bind in this library. The key comes first, the command goes in quotes, and anything you can type into chat can be attached this way.
Adds the actual weapon trigger to your attack chain. Without this line a tray bind fires your abilities but never pulls the trigger, which is a surprisingly common bug in home-made binds.
/bind space "GenSendMessage HUD_Root FirePhasers $$ +TrayExecByTray 0 0"