The Extension section in a horizontal pattern is executed after the Identification sections have completed and the CI has been identified. The Extension section allows adding additional attributes or relationships to the CI, or launching other patterns for further discovery12.
:
1: ITOM: Extending Discovery/Service Mapping Patterns - GlideFast ServiceNow
2: Horizontal Pattern probe - Product Documentation: San Diego - ServiceNow

The Discovery Dashboard provides a summary of the Discovery status, including the number of active discovery errors, the number of devices discovered, and the number of credentials used. Each error has a help link that provides more information about the cause and possible solutions.

The Duplicate CI Remediator is a feature of ServiceNow Discovery that helps to identify and merge duplicate CIs in the CMDB. It uses predefined rules and criteria to compare CIs across different data sources and determine if they are duplicates. It also provides a user interface to review and approve the suggested merges, or to manually merge CIs as needed. The Duplicate CI Remediator helps to improve the accuracy and quality of the CMDB data and reduce the maintenance efforts.
References:
* Duplicate CI Remediator
* Identify and merge duplicate CIs
* Duplicate CI Remediator rules