Field code
issue?.links[0]?.inwardIssue?.key

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

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

Read

Returned valueThe inward issue key of the first link, if no link is available, null is returned
Output data type

TEXT

Example outputPRJ-5

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