Hi,
I have a MacBook pro and a GK61 keyboard.
I have managed to remap successfully all the keys I wanted, except for the 'Menu' key of that keyboard.
I want to remap it to down arrow but that does not work.
Can you help me with that?
Thanks a lot
OS 10.15.3 (19D76)
MacBook Pro (Retina, 13-inch, Mid 2014)
Keyboard GK61 Mechanical Gaming Keyboard - 61 Keys Multi Color RGB Illuminated LED Backlit
From the Karabiner-Elements icon in the menu bar, open the EventViewer:

With the EventViewer open, press your Menu key. What "Name" does it show? That's the one you need to remap. For the Menu key, it usually is "application".
Thank you it helped me a lot and it works now. It was indeed the application key.
Thanks a lot, all good for me.
Most helpful comment
From the Karabiner-Elements icon in the menu bar, open the EventViewer:

With the EventViewer open, press your Menu key. What "Name" does it show? That's the one you need to remap. For the Menu key, it usually is "application".