Toying with the JSON editor when trying to use the combined mode I get:
Checkmk exception: Invalid graph specification type "combined" given Traceback (most recent call last): File "/omd/sites/home/lib/python3/cmk/gui/webapi.py", line 116, in page_api resp = _execute_action(api_call, request_object) File "/omd/sites/home/lib/python3/cmk/gui/webapi.py", line 207, in _execute_action return _execute_action_no_lock(api_call, request_object) File "/omd/sites/home/lib/python3/cmk/gui/webapi.py", line 221, in _execute_action_no_lock "result": api_call["handler"](request_object), File "/omd/sites/home/lib/python3/cmk/gui/plugins/webapi/graphs.py", line 35, in _get_graph return graph_spec_from_request(request) File "/omd/sites/home/lib/python3/cmk/gui/plugins/metrics/graph_images.py", line 235, in graph_spec_from_request graph_data_range, graph_recipes = graph_recipes_for_api_request(api_request) File "/omd/sites/home/lib/python3/cmk/gui/plugins/metrics/graph_images.py", line 197, in graph_recipes_for_api_request graph_identification_types.verify(graph_identification[0]) File "/omd/sites/home/lib/python3/cmk/gui/plugins/metrics/identification.py", line 49, in verify raise MKUserError(None, _('Invalid graph specification type "%s" given') % type_ident) cmk.gui.exceptions.MKUserError: Invalid graph specification type "combined" given
Not sure if that could help.