RotateDisplay

Rotate display of external monitor on macOS.

Usage

Download and open RotateDisplay.applescript with Script Editor
Modify parameter externalDisplay to your secondary monitor's name
Click Run the Script to test
Export as application, then you can rotate display by double click the app

FAQ

How to find my secondary monitor's name?

Click 🍎 -> System Preferences... -> Displays
The secondary monitor's name would appear on the title bar of popup window
- like "Acer CB281HK" in the screenshot below: