**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
"""Task Statistics"""
        allowed_dag_ids = current_app.appbuilder.sm.get_accessible_dag_ids(g.user)
        if not allowed_dag_ids:
            return wwwutils.json_response({})
        
        selected_dag_ids = {unquote(dag_id) for dag_id in request.form.getlist('dag_ids') if dag_id}
        if selected_dag_ids:
            filter_dag_ids = selected_dag_ids.intersection(allowed_dag_ids)
        else:
            filter_dag_ids = allowed_dag_ids
        
        running_dag_run_query_result = (
            session.query(DagRun.dag_id, DagRun.execution_date)
            .join(DagModel, DagModel.dag_id == DagRun.dag_id)
            .filter(DagRun.state == State.RUNNING, DagModel.is_active)
        )
        
        
        running_dag_run_query_result = running_dag_run_query_result.filter(DagRun.dag_id.in_(filter_dag_ids))
        
        running_dag_run_query_result = running_dag_run_query_result.subquery('running_dag_run')
        
        
        running_task_instance_query_result = session.query(
            TaskInstance.dag_id.label('dag_id'), TaskInstance.state.label('state')
        ).join(
            running_dag_run_query_result,
            and_(