User wants to create a filter to show for example issues that are open, with X version and all of those issues subtasks.
Today, you can search for issues subtasks by specifying the issues "parent".
ex of JQL code:
So, user wants to show all issues based on certain criteria and whatever subtasks these issues have, not a specific issues subtasks (without having to specify the issues "parent").
A known current workaround is documented at HowTo: Filter to show sub tasks of a filtered list of parent tasks .