@Elyhaka Nailed it! Thanks a lot, you made my day 
!
I had to disable networking.wireless to enable networking.networkmanager as stated in the comment of the documentation:
Note:
networking.networkmanagerandnetworking.wireless(WPA Supplicant) cannot be enabled at the same time: you can still connect to the wireless networks using NetworkManager.
Why is it not the default configuration.nix option?