Thank you all for the amazing replies. Steve Z, you nailed it. That's exactly what I'm looking for. JBfrom, emacs org-mode sounds like a great solution. I'm intrigued. It also looks a little compl...

Is there an app that displays keyboard-editable hierarchical structure in the left pane and text editing/word processing in the right pane? I'm looking for a Mac or web-based app that will allow me t...