Hello Tim,
I hope you are fine.
The OPC UA Connector publish data to the databus using the Common Payload Format.
Which means tag data is published as shown here: Tags Data
The OPC UA connector supports only one acquisition mode: CyclicOnChange.
This means it will publish only the tags whose values have changed. This means, your tag "mode" will appear in the JSON structure only when its value differs from the previous one.