What it's good for?
The external ID is used to uniquely identify the element for integration into third-party services. An external ID can be created on portal in section API. This External ID you can use in your queries/mutations.
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Adding new External ID:
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Select parent item and add name of External Identifier. When you click on Save so External ID is created.
Then you will see a list of created External IDs.
Example
Case study
Integration with Winshop - you can record billing action, etc
Case study
Integration of win..