You can configure a trusted connection between Kaspersky Sandbox and Kaspersky Endpoint Agent in the web interface of Kaspersky Sandbox server even when it is not included in the cluster.
If you have already merged the servers into a cluster, remove the server from the cluster, then create a new cluster based on this server and add all the servers intended for the Kaspersky Sandbox solution to the new cluster.
If the servers you need belong of another cluster, remove them from that cluster one by one and then add them to your cluster.
Installing and configuring a trusted connection between Kaspersky Sandbox and Kaspersky Endpoint Agent involves: