How to log top level json instead of into message with LoggingEventCompositeJsonEncoder?

Question

So using LoggingEventCompositeJsonEncoder I can do stuff like:

        <pattern>
          <pattern>{ "fieldName": "#tryJson{%message}" }</pattern>
        </pattern>

Generates { fieldName: [NESTEDJSONHERE] }

But how can I just generate a json at the top level instead of nested one level deep? e.g.:

        <pattern>
          <pattern>{ #tryJson{%message} }</pattern>
        </pattern>

generating { [JSONHERE] }