Link application audio to a specific output (wireplumber)

I’ve created a virtual mono audio sink with pipewire and wanted to link firefox to that specific virtual sink. The problem is that whenever I use the KDE audio settings and change the output, it never saves the changed output.

I tried using pavucontrol to no luck and checked “~/.local/state/wireplumber/restore_streams” to see that my settings are saved but its not apply to every new firefox audio window. (This thread How to assign an application its audio output in Wireplumber?)

I’ve also tried this github guide on creating a new lua config for wireplumber with no luck either: Make Wireplumber route Firefox' voice output to internal ALSA output · GitHub
All of my configs are in ./config/pipewire or ./config/wireplumber, any suggestions would be great thank you.