Saving a configuration saves uncommitted "state" changes on the Metadevice Editor's canvas. It does not save the current in-memory configuration. That is maintained by the state database replicas.
The save and restore configuration options enable you to create, in effect, a template configuration. This could be useful in configuring like machines: you create a configuration on one machine then copy to another, saving time in creating the second configuration.
The save and restore configuration options are also useful if you need to interrupt work, yet ensure that what you have configured so far (but not yet committed) will not be lost.