I am exporting disk and memory metrics on via cloudwatch agent for my autoscaling groups via following user data

yum update -y

yum install -y amazon-cloudwatch-agent

mkdir -p /opt/aws/amazon-cloudwatch-agent/etc

echo '{
  "agent": {
    "metrics_collection_interval": 60,
    "run_as_user": "root"
  },
  "metrics": {
    "append_dimensions": {
      "AutoScalingGroupName": "${aws:AutoScalingGroupName}",
      "InstanceId": "${aws:InstanceId}",
    },
    "metrics_collected": {
      "mem": {
        "measurement": [
          "mem_used_percent"
        ],
        "metrics_collection_interval": 60
      },
      "disk": {
        "measurement": [
          "disk_used_percent"
        ],
        "resources": [
          "/"
        ],
        "metrics_collection_interval": 60
      }
    }
  }
}' > /opt/aws/amazon-cloudwatch-agent/etc/amazon-cloudwatch-agent.json

/opt/aws/amazon-cloudwatch-agent/bin/amazon-cloudwatch-agent-ctl \
  -a fetch-config \
  -m ec2 \
  -c file:/opt/aws/amazon-cloudwatch-agent/etc/amazon-cloudwatch-agent.json \
  -s

The metrics are in cloudwatch via the CWAgent Namespace and i can visualise them via Browse Panels.

I am trying to add a empty Explorer widget with my custom metric but it shows No Data Available as shown below

Should anything else be configured?