You are absolutely correct, the Cloudera Manager configuration property within NiFi configurations fro logback.xml does require you to input the entire logbck.xml and then add your modifications.
Adding a new logger for the ControllerStatusReportingTask would require adding a logger like this:
<logger name="org.apache.nifi.controller.ControllerStatusReportingTask" level="DEBUG"/>
You can add this logger in line along with other loggers already in the logback.xml
The result would be all logging from this class at a DEBUG level and below would go in to the nifi-app.log.
You could optionally add an additional appender (NiFi has three existing appender now for the nifi-app.log, nifi-user.log and nifi-bootstrap.log files). You can copy and modify one of those and the your logger would need to look like this:
<logger name="org.apache.nifi.controller.ControllerStatusReportingTask" level="DEBUG" additivity="false">
If you found this response assisted with your query, please take a moment to login and click on "Accept as Solution" below this post.