MySensors Nodes: how to make the battery value a "diagnostic" type?

All, I am quite new to HA but I have a MySensors network with a Wifi-Gateway and many nodes running since years now. I “register” each node using the presentation() function and I send the battery values using sendBatteryLevel(). But these battery values a recognized as “normal” entities and not as “diagnostic” values as I saw it in other devices (see screenshot below) and as described under “Sensors” ==> entity_category: diagnostic`. Maybe not a big thing, but what is needed in my c++ code of the MySensors nodes to mark a sensor value as “diagnostic” value such as “Batterie” in the screenshot below? Thanks in advance.