Unable to update the tls-cipher-suites for node exporter in openshift 3.11
Openshift 3.11 seems to indeed be using openshift_cluster_monitoring_operator. This is why when you delete or change anything it recovers it to its defaults.
It manages node-exporter installation and it doesn't seem to allow for customizing node-exporter installation. Take a look at the cluster-monitoring-operator docs
My recommendation would be to uninstall openshift monitoring operator and install node-exporter yourself from official node-exporter repository or with helm chart where you actually have full controll over deployment.