Currently, the plugin submits a job to JES and checks for the job return code (max rc). If the return code is not zero, the plugin considers the job to have failed.
In real-life, non-zero return-codes do no necessarily mean that the jobs has failed. RC=4 (WARN) is usually considered fine, too. Under certain circumstances, even RC=8 may be considered fine (e.g. in delete steps when the dataset to be deleted does not exist).
To cope with these custom situations, the Submit JCL step should provide a way to specify the maximum return code which should be considered successful. Example: A max RC of 4 would mean that any job return code lower than or equal to 4 should be considered success.