As mentioned on the sketch (see link below), what I want to achieve is to have both lights going on and off (in unison) no matter which of the three switches (2 normal and a new intermediate) is flipped.
I am starting this fresh post on this question, now that I have sketched a new illustration showing which wires go where. I hope I have provided enough information in the new sketch:
I would like it to replace the existing double switch, and need to know which wires go to which terminals, etc.
Thank you again for any help.
Al