The DAGs main page has All/Active/Paused.

It would be nice if we can have also Running Now which will show all the DAGs that have at least 1 in Running of DAG runs:
![Screen Shot 2021-08-25 at 11 30 55](https://user-images.githubusercontent.com/62940116/130756490-647dc664-7528-4eb7-b4d8-515577f7e6bb.png)


For the above example the new DAGs tab of Running Now should show only 2 rows.
The use case is to see easily what DAGs are currently in progress.

]
    )
    @gzipped
    @action_logging
    @provide_session
    def graph(self, dag_id: str, session: Session = NEW_SESSION):
        """Get DAG as Graph."""
        dag = get_airflow_app().dag_bag.get_dag(dag_id, session=session)
        dag_model = DagModel.get_dagmodel(dag_id, session=session)
        if not dag:
            flash(f'DAG "{dag_id}" seems to be missing.', "error")
            return redirect(url_for("Airflow.index"))
        wwwutils.check_import_errors(dag.fileloc, session)
        wwwutils.check_dag_warnings(dag.dag_id, session)
        root = request.args.get("root")
        if root:
            filter_upstream = request.args.get("filter_upstream") == "true"
            filter_downstream = request.args.get("filter_downstream") == "true"
            dag = dag.partial_subset(
                task_ids_or_regex=root, include_upstream=filter_upstream, include_downstream=filter_downstream
            )
        arrange = request.args.get("arrange", dag.orientation)
        nodes = task_group_to_dict(dag.task_group)
        edges = dag_edges(dag)
        dt_nr_dr_data = get_date_time_num_runs_dag_runs_form_data(request, session, dag)
        dt_nr_dr_data["arrange"] = arrange
        dttm = dt_nr_dr_data["dttm"]
        dag_run = dag.get_dagrun(execution_date=dttm)
        dag_run_id = dag_run.run_id if dag_run else None
        class GraphForm(DateTimeWithNumRunsWithDagRunsForm):