Not sure, but in OrthancCPlugin.h file there is this. Those might be the events you can captture.
typedef enum
{
OrthancPluginChangeType_CompletedSeries = 0, /*!< Series is now complete */
OrthancPluginChangeType_Deleted = 1, /*!< Deleted resource */
OrthancPluginChangeType_NewChildInstance = 2, /*!< A new instance was added to this resource */
OrthancPluginChangeType_NewInstance = 3, /*!< New instance received */
OrthancPluginChangeType_NewPatient = 4, /*!< New patient created */
OrthancPluginChangeType_NewSeries = 5, /*!< New series created */
OrthancPluginChangeType_NewStudy = 6, /*!< New study created */
OrthancPluginChangeType_StablePatient = 7, /*!< Timeout: No new instance in this patient */
OrthancPluginChangeType_StableSeries = 8, /*!< Timeout: No new instance in this series */
OrthancPluginChangeType_StableStudy = 9, /*!< Timeout: No new instance in this study */
OrthancPluginChangeType_OrthancStarted = 10, /*!< Orthanc has started */
OrthancPluginChangeType_OrthancStopped = 11, /*!< Orthanc is stopping */
OrthancPluginChangeType_UpdatedAttachment = 12, /*!< Some user-defined attachment has changed for this resource */
OrthancPluginChangeType_UpdatedMetadata = 13, /*!< Some user-defined metadata has changed for this resource */
OrthancPluginChangeType_UpdatedPeers = 14, /*!< The list of Orthanc peers has changed */
OrthancPluginChangeType_UpdatedModalities = 15, /*!< The list of DICOM modalities has changed */
OrthancPluginChangeType_JobSubmitted = 16, /*!< New Job submitted */
OrthancPluginChangeType_JobSuccess = 17, /*!< A Job has completed successfully */
OrthancPluginChangeType_JobFailure = 18, /*!< A Job has failed */
_OrthancPluginChangeType_INTERNAL = 0x7fffffff
} OrthancPluginChangeType;
Stephen Scotti