How can I remap the Launchpad button?

Hi,
I'd like to use the Launchpad as an action in KM. How can I do that? (or is it not possible?)
(When I click on it to set the trigger a ? shows up and then it doesn't work)

(if it matters, I'm on an external keyboard)

Thank you,
Alex

FYI: I ended up using Karabiner-Elements to do this