If you create a filter that displays stories, you can add a column to the filter that displays a field called Sub-Tasks. Here's a sample:

Is there a similar field that would display a list of stories in an epic? I know I can set my jql to pull in all stories as line items, but I have a few users who just want to see the epics as line items, with a single column for each displaying a comma-delimited list of the stories in each epic.
If that doesn't already exist, is there a way to create a computed field that would provide this functionality?