How I can use labels with Mapping attributes?

[ilyavaiser]

Something about test.selector={{ index State.Config.Labels "com.docker.stack.namespace"}}

[canob]

Is there a way for this?
For example, I want to use the value of RUNDECK_NODE as the hostname:

        "Config": {
            "Hostname": "e55141745376",
            "Domainname": "",
            "User": "rundeck",
            "AttachStdin": false,
            "AttachStdout": false,
            "AttachStderr": false,
            "ExposedPorts": {
                "4440/tcp": {}
            },
            "Tty": false,
            "OpenStdin": false,
            "StdinOnce": false,
            "Env": [
                "RUNDECK_DATABASE_DRIVER=org.postgresql.Driver",
                "RUNDECK_DATABASE_URL=jdbc:postgresql://10.3.6.120/rundeck?autoReconnect=true&useSSL=false&allowPublicKeyRetrieval=true",
                "RUNDECK_DATABASE_USERNAME=postgres",
                "RUNDECK_NODE=rundeck1",

                ...

Is it possible?