A multi-cluster view can have exactly one connection to a local view. See Understanding Multi-Cluster Topologies for more complex topologies.

Adding a local view is simpler than a remote view, as the cluster already has access to the repository. To add a local connection to a multi-cluster view use the createLocalMultiClusterConnection():

mutation {
  createLocalClusterConnection(
    input: { multiClusterViewName: "myMultiClusterView", targetViewName: "humio" }
  )
}

This includes data from the local humio repo in the multi-cluster view.