I know this is a brilliant answer, I just don't understand it. Could you explain like I am a golden retriever?
I'll try. "Woof! Woof-woof! Woof-woof! Woof!" How was that?
Okay, serious answer: The two brake-light switches are wired in parallel, so either one can trigger the brake lights. Switches that are wired in series must all be closed at the same time for current to flow in a circuit, such as starter safety switches.
One side of both switches receives constant power (they're both fed from the same wire), and the other side of both switches runs to the brake light bulbs (both feed the same wire), and is only hot when you apply either (or both) brake(s).
What you want is an additional wire that is only hot when the front brake is applied, so you need to receive power from the front brake switch that the rear brake switch does not also trigger. So, insert a diode between the two brake switches.
A diode is a device that passes DC in only one direction, and are rated by (reverse) voltage and (load) current. Most diodes are marked with a triangle pointing at a band, or just a band alone. The banded end should point toward the load.
If you were to pull the switched wire (hot with brake applied) off of the front brake switch, and attach the wire to the strobe to the terminal, the front brake would only activate the strobe, and the rear brake would only activate the bike's brake light.
Get that so far?
Now, by putting a diode between the front switch's switched terminal and the bike's original switched wire, the front brake can simultaneously activate both strobe and brake lights, but the diode prevents the rear brake switch from activating the strobe.
If you hit only the front brake, current will flow both to the strobe (directly) and to the original brake lights (through the diode). If you hit only the back brake, current will flow to the original lights (directly), but not to the strobe (blocked by the diode).
