I think you are right about adding the second switch. connecting the DET button pin to ground through another switch would provide you a second way of triggering the detonation function.
I tried to put together a small code example of what I am trying to do. The two analogWrite() command in the loop() are what is required to drive my laser show.
I was wondering if it’s possible to attach a few buttons to the inputs of the Ardunio and code the script to allow me to move the lines on the screen to desired positions?