When you are trying to interconnect and assemble a set of issues (bugs, tasks, stories) it can be hard to gather them for bulk operations, like assigning them to the same EPIC or similar.
Well in Jira issue search field you can provide the following query:
issue in linkedIssues(issueKey)
This will give you a result listing all of the issues linked to the issueKey you provide.
In addition you can, do the following to refine the query, by providing an additional linkType, like so:
issue in linkedIssues(issueKey,linkType)
Ref: Atlassian Community