Can you control brightness on two monitors simultaneously via the brightness key? I have two Thunderbolt monitors daisy chained together and when I press down on the brightness key (F1/F2) it only dims the brightness / ups it only on one monitor. Is there a way so that when the brightness hotkey is pressed it can control both the monitors without having to open settings to control the other monitor?

Thanks.
This will not allow you to change them simultaneously but you can use


F1 or F2 for the main display and
control+F1 or control+F2 for the secondary display


As an addition you can also modify the brightness in smaller steps (1/4) by pressing option+shift with both combinations.