How do I send the fn keycode to macOS?

[travis (Travis Northcutt)]

I want to program a key to send the same keycode that my Macbook Air’s built in keyboard sends when I press the fn key on the built in keyboard.

I’ve looked through what appear to be the available keycodes here and I don’t see any that would make sense.

The screenshot below is what Karabiner EventViewer reports when I press this key.

[merlin (Michael Richters)]

You can’t, unfortunately. It’s not a USB HID key code of any sort, so external keyboards are not capable of sending it.

[travis (Travis Northcutt)]

Oh wow, interesting!

Out of curiosity, do you know how Apple’s own external keyboards send it? Some proprietary magic?