**Description**
In the trigger page, there is a text area to enter (optional) conf json. It would be great if a sample JSON can be provided programatically while defining DAG

**Use case / motivation**

This will improve usability of the UI that triggers a DAG

airflow/www/views.py
"""Multiple delete."""
        self.datamodel.delete_all(items)
        self.update_redirect()
        return redirect(self.get_redirect())
    def process_form(self, form, is_created):
        """Process form data."""
        formdata = form.data
        if formdata['conn_type'] in ['jdbc', 'google_cloud_platform', 'grpc', 'yandexcloud', 'kubernetes']:
            extra = {key: formdata[key] for key in self.extra_fields if key in formdata}
            form.extra.data = json.dumps(extra)
    def prefill_form(self, form, pk):
        """Prefill the form."""
        try:
            extra = form.data.get('extra')
            if extra is None:
                extra_dictionary = {}
            else:
                extra_dictionary = json.loads(extra)
        except JSONDecodeError:
            extra_dictionary = {}
        if not isinstance(extra_dictionary, dict):
            logging.warning('extra field for %s is not a dictionary', form.data.get('conn_id', '<unknown>'))
            return
        for field in self.extra_fields:
            value = extra_dictionary.get(field, '')
            if value:
                field = getattr(form, field)
                field.data = value
class PluginView(AirflowBaseView):