If you add a new directory to the VMware Identity Manager service after you have already deployed a cluster for high availability, and you want to make the new directory part of the high availability configuration, you need to add the directory to all the instances in your cluster.
In an on-premises deployment, you do this by adding the connector component of each of the service instances to the new directory. In a SaaS deployment, you do this by adding all the connector instances to the new directory.