GNOME Shell Volume Mixer
Shell Volume Mixer is an extension for GNOME Shell allowing separate configuration of PulseAudio devices and output switches. It features a profile switcher to quickly switch between pinned profiles and devices.
Middle mouse click on a slider mutes the selected stream.
That's it. Add the resulting archive via GNOME Tweak Tool (extensions tab) or copy it's content manually to ".~/.firstname.lastname@example.org".
GNOME Settings Daemon (GSD)
GSD hardcodes the step for each key press of volume keys to 6% of maximum volume. While this might be OK for most people, some would prefer a configurable setting. There's a bug in GNOME's tracker which, according to the comments by developers, won't ever get fixed in a way that could allow configurable volume steps.
Shell Volume Mixer tries to grab GSD's hotkeys to provide configurable steps for sliders and media keys.
This is a fork of AdvancedVolumeMixer by Harry Karvonen (git://repo.or.cz/AdvancedVolumeMixer.git). Many thanks go out to him for his initial work.