Seems more like a Network Manager topic, moving to Off Topic.
Is there a way to set default args for openvpn?
I know little about NM but by editing the service file (openvpn-client@.service) you can achieve what you want.
[Service]
ExecStart=/usr/bin/openvpn --mute-replay-warnings --config %i.conf
After an update the change will be lost though.
There might be a way to make that permanent, don't know...
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