Option to collapse/expand all in a section

When in the left-hand navigation pane, I would really love to be able to right-click a book, or part, or chapter and choose to expand/collapse all items from that point downwards. Doesn't even need to be a right-click option -- a keyboard shortcut would be fine!

It's a small change that would save me a lot of time, since I like to have everything collapsed except the part (or chapter) that I'm working on.

I know that there is currently the ability to expand/collapse a chapter/part to quickly hide by using the arrow expand/collapse icon, but when you revert to the original state Dabble will remember all the subitem statuses -- chapters in a part will still be open, etc. This is sometimes perfect for my needs. But other times I just want to collapse *all* child items in a tree--if a file tree is a mess of open chapters, I don't want that mess staring at me until I manually collapse every chapter. Hope that makes sense!