Is it possible to adding fields to beats monitoring data?

[Bingu_Shim]

Hello

Currently I'm operating about 1,000 beats, and It will grow soon.

So, I'm trying to make few Dashboards for managing and monitoring beats status.
I found these setting, and I was able to gathering the beats status data to my Elasticsearch cluster which is only for monitoring purpose.

monitoring:
   enabled: true
   elasticsearch:
      hosts: ["my-monitoring-escluster.mycompany.com:9200"]
 ...

While I making dashboard I was looking for a way to group these monitoring status by projects(or services). So, I tried the following, and I doesn't work.

monitoring:
   enabled: true
   elasticsearch:
      hosts: ["my-monitoring-escluster.mycompany.com:9200"]
      fields_under_root: true
      fields:
          project.id: 1023
          service.id: abcd
 ...

Is there any way to add fields(only for grouping) to the beats monitoring data?