I'm trying to modify [vpn-secrets], as mentioned here:
https://askubuntu.com/questions/198136/error-when-trying-to-connect-to-vpn-on-startup
However, nmcli complains about it,
%> sudo nmcli con modify myvpn vpn-secrets.data 'password = xxx'
Error: invalid or not allowed setting 'vpn-secrets': 'vpn-secrets' not among [connection, vpn, ipv4, ipv6].
Is it impossible to change the password with nmcli?