WTH can't I adjust the brightness only of lights that are already on?

Month of "What the heck?!"
1

If I have a group of lights, some are on, some are off - there’s no easy way to adjust the brightness only of those lights that are on! A simple call to adjust the brightness will adjust the brightness on all lights - including those that are off.

There’s a technical discussion of this issue here:

2

Closing duplicate, please vote here: WTH can't light groups only dim lights that are on Hue-style