center pin is signal on the triggers.
if you remove the triggers and solder to the controller pcb you add a 10k resistor to bypass the assembly to connect a arcade button to it.
looking at the link that pinout setup is horrible.
find another pcb pinout elsewhere as that one sucks and not very detailed at all.
like on the alternative side...OK so what it what the author forgot to add what they even were in that pic. you just guess solder them points and hope you guess them right I guess
