Sub-issues can be very helpful, but currently they are very hard to manage because there does not seem to be any way to filter them.

For example, if I am using a filter that displays issues that 1) have a certain tag, and 2) are "assigned", and a parent issue matches those criteria, none of the matching sub-issues will appear in the top level search, and expanding the parent issue displays ALL sub-issues, regardless of if they meet the filter criteria.

It would be merciful to at least have an option for a filter to operate on all tickets as if they were top-level.