Setup>Audio>PAFL Additive mode: On
PS, if you turn this on, it’s probably worth adding a PAFL clear function to one of the softkeys on the surface (Setup>Control>Softkeys Select a softtkey, Function:PAFL clear) so you don’t have to go hunting through layers to find that one channel\bus that’s still PAFLed.
PPS, if you’re wanting to listen to a whole lot of BVs together and have their levels and FOH panning in the cans (if applicable), Setup>Audio>PAFL Input AFL: On. Of course the downside to this is that the AFL setting applies to all your inputs, which means you can only PAFL inputs that have their LR fader up.