Kanban - Allow Changing Sub-tasks' Ranks Independently

I keep my Kanban columns sorted by Rank, but if I have sub-task JIRAs, the board UI forces sibling sub-tasks to be grouped and only allows you to change their Rank among their sibling sub-tasks. The only way I've found to change sub-tasks' Rank is by changing the Rank of their parent task.

For example, I have these tickets:

LAYOUT-5541 - regular ticket
PENGDEV-153 - parent ticket
PENGDEV-155 - sub-task of PENGDEV-153
PENGDEV-156 - sub-task of PENGDEV-153

My board always displays PENGDEV-155 and PENGDEV-156 next to each other, so I can't rank my tickets like this:

1) PENGDEV-155
2) LAYOUT-5541
3) PENGDEV-156

This is a pretty big pain. Or is there a way to do this that I just haven't found?