How to: AirVPN WireGuard connection with Ubuntu Network Manager

[zaGGiuZU 0]

I happily used the guide for WireGuard connection from terminal on my Ubuntu laptop.
https://airvpn.org/linux/wireguard/terminal/

However I wanted a 'clickable' solution with Ubuntu Network Manager. I tried to fill the fields for WireGuard connections, but it did not work.
I almost give up but found a terminal command to import the downloaded configuration and after the created connection was working as good as the terminal version.

nmcli connection import type wireguard file ./Downloads/wg.conf

It creates a "wg" VPN connection. Feel free to edit it from the Network Manager GUI.

Disclaimer:
I found the idea in the comment section under the following page:
https://www.xmodulo.com/wireguard-vpn-network-manager-gui.html

Comment from Eugene:

Thank you for the great manual! However, here are some additions.

1) You shouldn't add "gateway" in IPV4 settings.
2) It's better to import .conf file using cli:
$ nmcli connection import type wireguard file YourConfigFile.conf
3) It's better to turn off automatic connection using GUI/CLI after. That's why you're using GUI: to connect manually when needed.
4) You need NM to enable managing wg0 interface. Or you'll get "wg0 is strictly unmanaged' error:
# cp /usr/lib/NetworkManager/conf.d/10-globally-managed-devices.conf /etc/NetworkManager/conf.d/
Then edit /etc/NetworkManager/conf.d/10-globally-managed-devices.conf and add except:type:wireguard:
unmanaged-devices=*,except:type:wifi,except:type:gsm,except:type:cdma,except:type:wireguard

* Also this input box needs to be fixed: on each clipboard paste it doubles caret return and adds empty lines which multiply on and on in Firefox.