This is one of those probably simple things that I just cannot get my head around (maybe lack of coffee).
I'm building a circuit that has a standard wired stomp 3PDT for Bypass. The wiring I use is this:
(http://1.bp.blogspot.com/-k5Sh68yVU18/TzGRFKbiALI/AAAAAAAAAlk/CbfaaduUjYQ/s1600/!Offboard+wiring.png)
I also need to include another 3PDT switch that simply makes a connection in the circuit, on or off (it's Octave On/Off), so just two wires for this. This should have its own LED to indicate on or off. (I know I could use a DPDT but I don't have one).
I know how to wire them so the LEDs have their own make/break loops but I want the Octave LED to switch off when the Bypass stomp is off.
For your octave led, instead of wiring the 2nd switch to connect it to ground, wire it to connect it to the negative leg of D1 in your diagram. That way it will only get connected to ground if D1 is also connected to ground. And that will only happen when your circuit is on.
That's it! Thanks!
Time for coffee!