¿Cómo agregar un atajo de teclado para alternar F1, F2, etc. como teclas de función estándar?

Para asignar un atajo de teclado a este script, puede crear un servicio en Automator.

Debes cambiar Service receivesa no input. Luego agregue Execute AppleScripty pegue su script. Guárdalo en ~/Library/Services.

Una vez guardado, debes ir a System Preferences → Keyboard → Shortcutsy puedes averiguarlo en Services → General. Asigne su atajo preferido allí.

Con Karabiner , puede guardar este archivo como ~/Library/Application Support/Karabiner/private.xml:

<?xml version="1.0"?>
<root>
  <item>
    <name>fn+escape to toggle f-keys</name>
    <identifier>fnesc</identifier>
    <autogen>__KeyToKey__ KeyCode::ESCAPE, ModifierFlag::FN | ModifierFlag::NONE, KeyCode::VK_CONFIG_TOGGLE_fkeys</autogen>
  </item>
  <item>
    <name>fkeys</name>
    <identifier vk_config="true">fkeys</identifier>
    <autogen>__KeyToKey__ ConsumerKeyCode::BRIGHTNESS_DOWN, KeyCode::F1</autogen>
    <autogen>__KeyToKey__ ConsumerKeyCode::BRIGHTNESS_UP, KeyCode::F2</autogen>
    <autogen>__KeyToKey__ KeyCode::EXPOSE_ALL, KeyCode::F3</autogen>
    <autogen>__KeyToKey__ KeyCode::LAUNCHPAD, KeyCode::F4</autogen>
    <autogen>__KeyToKey__ ConsumerKeyCode::KEYBOARDLIGHT_LOW, KeyCode::F5</autogen>
    <autogen>__KeyToKey__ ConsumerKeyCode::KEYBOARDLIGHT_HIGH, KeyCode::F6</autogen>
    <autogen>__KeyToKey__ ConsumerKeyCode::MUSIC_PREV, KeyCode::F7</autogen>
    <autogen>__KeyToKey__ ConsumerKeyCode::MUSIC_PLAY, KeyCode::F8</autogen>
    <autogen>__KeyToKey__ ConsumerKeyCode::MUSIC_NEXT, KeyCode::F9</autogen>
    <autogen>__KeyToKey__ ConsumerKeyCode::VOLUME_MUTE, KeyCode::F10</autogen>
    <autogen>__KeyToKey__ ConsumerKeyCode::VOLUME_DOWN, KeyCode::F11</autogen>
    <autogen>__KeyToKey__ ConsumerKeyCode::VOLUME_UP, KeyCode::F12</autogen>
    <autogen>__KeyToKey__ KeyCode::F1, ConsumerKeyCode::BRIGHTNESS_DOWN</autogen>
    <autogen>__KeyToKey__ KeyCode::F2, ConsumerKeyCode::BRIGHTNESS_UP</autogen>
    <autogen>__KeyToKey__ KeyCode::F3, KeyCode::EXPOSE_ALL</autogen>
    <autogen>__KeyToKey__ KeyCode::F4, KeyCode::LAUNCHPAD</autogen>
    <autogen>__KeyToKey__ KeyCode::F5, ConsumerKeyCode::KEYBOARDLIGHT_LOW</autogen>
    <autogen>__KeyToKey__ KeyCode::F6, ConsumerKeyCode::KEYBOARDLIGHT_HIGH</autogen>
    <autogen>__KeyToKey__ KeyCode::F7, ConsumerKeyCode::MUSIC_PREV</autogen>
    <autogen>__KeyToKey__ KeyCode::F8, ConsumerKeyCode::MUSIC_PLAY</autogen>
    <autogen>__KeyToKey__ KeyCode::F9, ConsumerKeyCode::MUSIC_NEXT</autogen>
    <autogen>__KeyToKey__ KeyCode::F10, ConsumerKeyCode::VOLUME_MUTE</autogen>
    <autogen>__KeyToKey__ KeyCode::F11, ConsumerKeyCode::VOLUME_DOWN</autogen>
    <autogen>__KeyToKey__ KeyCode::F12, ConsumerKeyCode::VOLUME_UP</autogen>
  </item>
</root>

Luego abra la aplicación Karabiner, presione el botón ReloadXML y habilite la configuración.