Can't add virtual output devices. Was possible some time ago. Says in KCM: "Requires module-gsettings PulseAudio module" The package https://packages.ubuntu.com/cosmic/pulseaudio-module-gsettings is not available on KDE Neon / Ubuntu 18.04.
iirc neon builds it with gsettings but only has gconf or something.
Yea, I tried to install the gconf one. But it was already installed.
pulseaudio-module-gsettings is available in Neon 20.04