Can I assign separate brightness shortcuts to individual displays?

Yes. Create a macOS Shortcut using a BetterDisplay action with an explicit Display parameter, then assign that Shortcut a keyboard combination. Make a separate Shortcut for each display and adjustment you want.

For a pair of brightness-up and brightness-down shortcuts:

1. Open Apple’s Shortcuts app, create a new Shortcut and search for BetterDisplay actions.
2. Add Image Adjustment Offset, choose the intended Display, and select Brightness as the Feature.
3. Set Offset Value to a positive value such as 5 to raise brightness, or -5 to lower it. The value is a percentage of the control’s range, not a percentage of its current level.
4. Run the Shortcut to confirm that it adjusts the intended display. The display must be available and support the selected control.
5. In the Shortcut’s details, choose Add Keyboard Shortcut and press the combination you want. Apple’s keyboard-shortcut instructions describe the assignment.

Duplicate the Shortcut for the opposite direction or another display, changing the offset, target and keyboard combination. If you want a fixed level instead, use Set Brightness with its display and brightness parameters. Hardware-only and software-only adjustments are separate feature choices when you specifically need those controls.

Assigning a Shortcut to a display does not distinguish the same key pressed on two different physical keyboards. BetterDisplay’s normal target rules follow screens, not keyboard identity. A separate keyboard utility would need to distinguish the devices and invoke the corresponding display-specific Shortcut or script.

These explicit display actions are useful when you want a fixed target regardless of pointer position. BetterDisplay’s ordinary brightness-key target preferences instead follow the pointer, focused window or all suitable screens. The Shortcuts reference lists the available actions and parameter conventions.