Now I have no headlamp, no taillight (unless brakes are applied) and the starter button doesn't work. I have a male black/red, a female brown red, and a brown blue from the buzzer that are all without pairs.
The black/red is another bar control circuit (right side) taking power from the starter button, which powers either the headlight or the starter solenoid from the black wire. Black/ red is internal harness joined to the Br/red, providing power to the Headlight fuse.
Brown/blue would go to turn buzzer, if you have one, or left unconnected if you don't. Female connectors can be left dangling.
Brown/red is headlight power which routes from Fuse block to bar control Hi/Lo switch. Which of those is nearer to the wire you have loose? I suspect since it's female, it should go to the bar control harness.
Methodology:
Wires unplugged and hot would have a female connector, to avoid making a grounding contact if it vibrates apart. So, what you have is likely sourced from the fuse block, to be connected to the headlight Hi/Lo switch.
Tail light is the BR circuit, routes from Key switch to tail. You have the Brown plugged into the harness?
Cheers,
