Switching alt key for command key - logitech k750 on (os x 10.11.3)

I'm just trying to set mac layout on my logitech k750 keyboard so alt works as command key and (windows) command key works as alt key.

I tried to use "Preferences > Keyboard > Modifier keys > Unifying Device" where I switched option key for command key, but that doesn't have any effect.

Any idea?

2 Answers

I used Karabiner-Elements for this. It works well too. Download it here.

Not sure about the 750 keyboard but on my 850 press and hold FN-O for three seconds to switch to mac mode. That swaps the Alt and command keys amongst other things.