Corkboard navigation

I like to develop a project in a topdown way using the corkboard. I start with a “seed” for the story, a synopsis of the story on one card. Then I break that seed down at the next level into two or more cards, each containing a synopsis of that part of the story. I break each of these cards down the same way, as needed. Eventually, the leaves of this tree structure, taken in sequence, comprise the complete “treatment” of the story. What I need is a way to navigate up and down through this tree structure directly in the index cards. In the Right Button Menu, selections for “Up Level” and “Down Level” would work, with accompanying keyboard shortcuts.

To drill down a level, you can double-click on the corkboard icon or select opt-cmd-O. To go back up a level, you can then just hit the “back” key (cmd-[).
Best,
Keith