It's a Firefox extension for just me. [0] I've posted it here before, and one user said they'd start using it. I hope someone else finds it useful again. The problem: I wanted to be able to mute League of Legends streams in between games with a hotkey, and without changing visibility of any windows in the process of doing so. This is a much harder problem than you'd think, even with the existence of Autohotkey, and NirCmd, and ControlSend, because Firefox is really annoying. [1] It ended up requiring me to write an entire Firefox extension as well as use an AHK that uses ControlSend.
Anyway, yeah, that FF extension. It represents the culmination of about 5 years of me trying to solve this problem with progressively more complex and incrementally better solutions until I finally arrived at a ridiculously over-engineered version that actually works as it should.
[0] https://github.com/RheingoldRiver/MuteTabsMatchingPattern
[1] https://river.me/blog/global-hotkey-mute-firefox-stream/