That eliminates the "easy" options. The rest will be tracing/measuring the wire harness.
Do you have a diagram for the lighting system? Mine shows that the power supplying the brake pedal switch via an orange wire (Fuse 23). If that brake pedal switch is intact and functioning, the power is then sent to the mutlifunction switch is via a white wire. Everything after that is within the switch and then the body wiring downstream of the switch.