How to make drone downstream plugin emit `custom` event instead of `push`

I have a downstream step after a npm package publish which will trigger linked repositories and my intent was to, within the downstream triggered build, update the npm package MODULE_NAME and then commit again to the parent repository, which would then trigger a second build on the child repository, with the updated dependency.

The problem is that the downstream plugin is dispatched with the push event, so it’s really like any other build for the linked repository. I was expecting the downstream plugin to trigger the custom event, so I could have a separate pipeline only for dealing with those updates.

How would you advise achieving this behaviour without transforming the main pipeline into conditional maze, checking environment variables provided by the plugin?

thanks in advance

# main pipeline

  - install
  - build
  - test
  - deploy

  event: {exclude: [tag, custom]}


# downstream pipeline

  - 'npm update $MODULE_NAME'
  - git commit -m "build: update $MODULE_NAME dependency"
  - git push origin "$DRONE_BRANCH"

   event: [custom]

Just an update on my previous question.
I believe for simulating something that behaves on a similar fashion, deployments would work as expected. So:

  - name: downstream
    image: plugins/downstream
      fork: true
+     deploy: upstream
+     last_successful: true
        - ...

And then, on the downstream repository I could enable a pipeline that activates on upstream targets only.

kind: pipeline
name: default


-  event: {exclude: [tag, custom]}
+  event: {exclude: [tag]}
+  target: { exclude: [upstream] }


kind: pipeline
type: docker
name: self-update

  - npm install ${MODULE_NAME}
  - git commit -am "build: update $MODULE_NAME dependency"

-  event: [custom]
+  target: [upstream]