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”

https://support.obsidiancontrol.com/Content/Playback/Cuelist_Directory/Cuelist_Directory_Special_Functions/As_Main.htm?Highlight=main

Yes! thank you!