This is a great example of why I like the Touch Bar on my Macbook Pro. When it is connected to an external monitor, I tap the brightness icon in the Touch Bar and get two sliders: one to control brightness on my laptop, and one to control brightness on my external monitor. This seems to be a native feature; I did not install anything to do it.
But why can't they expose these controls independent of the Touch Bar? I actually find it ridiculous as a 2015 MBP owner that there is no easy native way to do this basic thing unless, apparently, you have a Macbook with a Touch Bar
F1-F2 to change MBP brightness, CTRL+F1-F2 to change external monitor brightness. Works with my thunderbolt LG 5K. (I dislike the Touch Bar so I always use an external keyboard when at my desk)
They are independent of the touch bar. It simply presents a UI for any external monitors for which macOS already knows to control the brightness. You can change the brightness of supported monitors from System Preferences or using the keys on compatible keyboards.
I agree. There are brightness sliders for each screen in System Preferences, but doing it that way is a pain in the butt for something that I do frequently.
My previous laptop was a 2012 Macbook Air, and I used an Apple Bluetooth keyboard at my desk in part for this reason. The laptop keyboard adjusted the laptop screen brightness, and the BT keyboard adjusted the external screen brightness.
Mine is an old Apple Thunderbolt 27" external display.
It didn't occur to me that the Touch Bar control might be specific to this display, since the display predates the TouchBar by many years. But maybe it is, since you and other commenters don't seem to see it.
See, my granny would have a hard time with this because while us young folk can control two sliders at once with ease, she would go as crosseyed as dead ol' Bessie was when we found her out back last year. Apple seems to expect more and more of us - soon we'll all be forced to be DJ's just to use our cell phones (har har!)
