Modify json tiddler with actions

Following this discussion about auto-adding a new tag bibtex-entry after importing bibtex in the RefNotes plugins.

actions in the widget $dropzone is triggered after converting bibtex into tiddlers, and before display the import button on the import tiddler.

In this step, the json tiddlers are generated int he import tiddler, for example

{
    "tiddlers": {
        "paper_1": {
            "title": "paper_1"
        },
        "paper_2": {
            "title": "paper_2"
        }
    }
}

Not I am not sure how to add a new field tags into each tiddler.

$action-setfield with $index can only add field in the root of json.

<$action-setfield $tiddler="ImportBibtex" $index="tags" $value="bibtex-entry"/>

So my question is how I should add a new field in each tiddler? That is

{
    "tiddlers": {
        "paper_1": {
            "title": "paper_1",
            "tags": "bibtex-entry"
        },
        "paper_2": {
            "title": "paper_2",
            "tags": "bibtex-entry"
        }
    }
}

I think JSONMangler has the most complete set of tools available for modifying JSON tiddlers.

The pre-release 5.2.4 may contain features that will help with this. Of course a JSON made into a plugin means the tiddlers are accessible as shadow tiddlers you can overwrite these, using normal set field and tag operators etc… and then rebuild the contents of the original JSON/Plugin tiddler.