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A dashboard is shown as a dependency of the custom field if the dashboard gadget has a property of custom field type, and its value is the name or ID of the field.
Usage in
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service projects
Dependency is detected when the custom field is referred to in Request types, Queues, SLAs, or (Legacy) Automation rules. Usage detection happens when the service projects' cached index is generated for the first time or when it’s refreshed.