Call Service Node: How do we utilize the Merge Data feature to override a value?

I’m simply attempting to set the entity/entities that the Call Service node will target before the payload hits the Call Service node, rather than creating a service call node for every entity when needed.

The purpose for this is to programatically select the media player that will be called depending upon the type of event that’s coming through.

In the Service Call Node, there’s reference to “merging” the payload.data to override the configurations, but there’s no clarity on how to do it.

In the node, my Data field shows the following:

{
    "media_content_id": "{{{payload}}}",
    "media_content_type": "audio/mpeg",
    "announce": "true"
}

The node is set with:

Domain: media_player
Service: play_media
Entity: media_player.picoreplayer2

Then the data above.

If I were to remove the entity from the node and add the following, would it work?

{
    "media_content_id": "{{{payload}}}",
    "media_content_type": "audio/mpeg",
    "announce": "true",
    "entity_id":"media_player.picoreplayer2"
}

This works. I should have tested it before I posted the question.