Question
What is the difference between Add tags and Set tags in business rules?
Answer
The Add tags action in both triggers and automations allows you to add one or more tags to the existing tags that are already assigned to your ticket.
The Set tags action removes all existing tags and replaces them with the tags you select in your business rule actions.
Warning: Only use the action Set tags in situations where you want to remove all of the previous tags on the ticket. Removing tags can be disruptive to your workflows and reporting unless it is intentional. Zendesk recommends the action Add tags in most setups.
For more information about the different action statements, see the article: Trigger conditions and actions reference.