CheckMK Raw with Grafana - Combined Graph: Graph field not selectable

[BH2005 (Bernd Holzhauer)]

as I had writen

@BH2005

if you want to create the combined graph in Grafana you have only the restrictions of Grafana

then you have just the limitations of Grafana.
I have also the Connector for Grafana in Service (just for testing) and it work as expected.