Add fields do not work Winlogbeat

Hello,

I would like to add fields in _source by using fields config, and also I tested with pocessors.
But I don't even see the fields that I wanted to add

Processors config

processors:
  - add_fields:
      target: _source
      fields:
        env: staging
        agent:
          type: agent.type
          version: agent.version
          ephemeral_id: agent.ephemeral_id
          id: agent.id
          name: agent.name

Fields config

fields_under_root: true #I also tried with false
fields:
  env: staging
  agent:
    type: agent.type
    version: agent.version
    ephemeral_id: agent.ephemeral_id
    id: agent.id
    name: agent.name

And here is a screenshot of the result in Kibana


Thank you for your help, I really need this, it's been 4 days I am on it

_source is an Elasticsearch concept and doesn't apply for Beats at that level of ingest.

I would try adding it to message instead, as it will then show up in _source when it gets to Elasticsearch,