I am a pianist and musical producer, B.mus Tel Aviv university.
There are no professional extensions for browsers which are parametric, graphical EQs.
The best I’ve found is Ears Audio Toolkit for Chrome and it has it’s disadvantages.
I would like an extension which operates on every page, has DB levels, Q levels, Frequency levels, and has the option to add bands. ikjb qrange is a model which could be employed.
I believe there will be a need.
I would like to also put inside the equalizer a tone generator, so one could sweep the frequency range, correct it, and then enjoy a full listening experience (most headphones are changing the EQ range, which creates an experience the producer didn’t mean).