M-PLAY - Led on MAIN GO Section

hi, sorry for my english.
I know that Main GO button and Back/pause button on M-PLAY have a led blinking when pressed (I know that because I used this function months ago).
now, I don’t remember how to re-activate this function.
could you help me? thank’s in advance

I think they light up when a cuelist is set to “As Main”


Yes! thank you!