$ nmcli --offline conn add type ethernet ens3 ipv4.dns 192.168.1.1 \ >output.nmconnection
$ nmcli --offline connection modify ens3 ipv4.dns 192.168.1.1 \ <input.nmconnection >output.nmconnection
The is what was suggested by Beniamino in https://bugzilla.redhat.com/show_bug.cgi?id=1361145, because I liked it.
It is currently useful for completely offline operation e.g. in kickstarts.
Once an ability to import/export keyfiles gets implemeneted, it would be possible to integrate the offline commands with the running service. This patch set doesn't implement that.