Adding customised kibana filtering tag ( such as Kubernetes.cluster.name)

I have deployed ELK system to monitor kubernetes clusters logs from different data-centers and environments. I would like to be able to filter logs based on cluster's name. Is it possible to add my own customize tag (variable) to elastic search or Kibana tags so it will filter logs base on that.
For example I want to add kubernetes.cluster_name tag to fields in Logstash* so I can create a dashboards based on that tag.

Any assistance would be greatly appreciated.

Joshua.

Are you trying to add this field at index time or on already indexed data?

At index time, you can use a Logstash filter to add the new field based on other data. https://www.elastic.co/guide/en/logstash/current/plugins-filters-mutate.html#plugins-filters-mutate-add_field

On existing indexes, you could use the Update By Query API to add a field based on the existing fields or _source. See Pick up a new property.