A developer defines new log fields using the Add Log Fields activity.

The Add Log Fields activity adds custom log fields to the Robot Execution Logs, which are included in every Log Message execution throughout the entire workflow1. The custom log fields can be useful for adding more information and visibility to the logs, especially for transactional data processes2. However, the custom log fields are not permanent and can be removed by using the Remove Log Fields activity, which takes the name of the custom log field as an input1. The Remove Log Fields activity is usually placed at the end of a transaction, to reset and remove the custom log fields for the next transaction2. Therefore, the custom log fields will stop being added to the robot execution logs when a Remove Log Fields activity is used to remove them.

https://docs.uipath.com/activities/other/latest/workflow/add-log-fields

https://www.uipath.com/community-blog/tutorials/add-log-field-advantages