Monitorian
A Windows tool to easily adjust brightness of multiple monitors
...It supports both built-in laptop screens and external monitors, allowing adjustments either on a per-monitor basis or all together at once, making it especially useful for multi-monitor setups. The app displays sliders for each connected monitor, and on systems with ambient light sensors it can show both the configured brightness and the sensor-adjusted brightness to help you fine-tune lighting according to your environment. Monitorian also lets you adjust the range of brightness and contrast values for each monitor so you can set custom limits that better match your preferences. Usability features include gesture support on precision touchpads and easy renaming of monitors to keep them organized in the UI. ...