On Windows you can use the TAB key to switch between which button has focus then press space to click the focused button.
However, on MacOS, when presented with the dialog in this screenshot, I cannot seem to use tab to switch between the buttons I want to click. I can only hit RETURN to click the Save button, or ESC to click Cancel. But I have no idea how I can click the "Don't Save" button using just the keyboard.
How can I navigate/click buttons in a MacOS message box using just the keyboard (not the TouchBar, Mouse or TrackPad)?