This request stems from the inability to see the same information on a standard issue with sub-tasks as you can on a standard issue without sub-tasks when stories are used as swimlanes. There is an existing request, GHS-5397, to modify this functionality.

In the absence of GHS-5397, an alternative/supplemental solution would be to grey out or otherwise mute issues that are not sub-tasks to the selected parent issue. Our team makes heavy use of sub-tasks and JIRA Agile. However it is difficult to see which sub-tasks are associated with the parent issue at a glance. Especially when there are a large number of issues in the sprint each with their own sub-tasks. This would let you quickly scan the work mode for the status of the sub-tasks without needing to open up the issue details for each one.