When clicking on a taskbar button (and there are multiple associated windows for that button), there's a noticeable animation until the next step is clickable.

Is there any way to decrease this animation time? I couldn't find it in the settings dialog, but I'm guessing it's in a config file somewhere...

Desktop Effects > Sliding Popups

Edit: There's also an "Animation speed" slider somewhere, not sure where.

Not for the menu.

Hmm it looks like the one in this case is:
Desktop Effects > Present Windows

I don't want to turn the effect off, just decrease the animation time. However I don't see an option to decrease it, does it live in a config file somewhere?

Ah I remember, Display & Monitor > Compositor > Animation Speed: Instant
Anything faster than the default is near instant.

Perfect, thankyou! Never would I have thought to look for this setting under "Hardware".