On the above shown asking popup window on Mac, how can I select another button (left button) by using keyboard. Without clicking mouse button, I want to make left button highlighten. Is there any shortcuts?
Go to Preferences -> Keyboard. At the bottom, turn on "All controls" under "Full Keyboard Access".
The alternate option will be highlighted with a blue ring. Hitting space will activate this. If there are multiple options, hitting tab will alternate between them.