How can I change BetterDisplay’s language without changing the Mac’s language?

Use macOS’s language preference for individual apps. Open System Settings > General > Language & Region, then find Applications and add BetterDisplay with the language you want, such as English.

If BetterDisplay is already listed, select its entry and change the language. Quit and reopen the app so the preference takes effect. Choose a language supported by the app.

This is useful when following an English guide or preparing screenshots for support. To return to the normal system choice, remove BetterDisplay’s individual language entry. See Apple’s app-language instructions.