It also works when using Spotify Connect on your iOS device. If you can use your volume buttons to control it you can also adjust it with the slider in the control centre.
That's really helpful to know. At this point though, I'm excited enough to build a volume knob that I'll probably still do it.
edit: After trying this out it a bit, it's definitely an improvement over the small sliders and a huge improvement over the stepped volume changes from the buttons, but I'm still left wishing I could make use of more than ~10% of the slider's full range.
