Similarly to Sketch, especially because Subform is a design tool that depends a lot on hierarchy, I think it would make sense to wire the ESC key to take you up the hierarchy by selecting the parent layer when pressed.
It has become a very important part of my workflow, together with the tab and enter keys, which allow you to move across the entire hierarchy without touching your mouse.
Currently, the enter key is wired to creating a new layer. I suppose that this is a temporary measure, so once the enter key frees up again I'd strongly suggest you consider this approach.