Field code
issue?.links[0]?.type?.id

Links are stored in lists. Documentation on how to work with lists can be found here.

You can access the whole link type by issue?.links[0].type which returns an Issue link object, issue?.links will return a list of objects.

Read

Returned valueThe ID of the issue link type. If no links are available, null is returned.
Output data type

NUMBER

Example output10002

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