I'm late for a meeting so I just say couple of things.<p>This looks really good and sounds even better! I have invested a considerable amount of time in exploring visual XML document editing, including contentEditable, RelaxNG, web components, textarea input redirection (CodeMirror), especially for DocBook XML.<p>I'm curious have you thought about things like non-textual (for the writer) elements like widgets for dates, how to edit attributes, types in general (only numbers here).<p>In the comments here you mention douple enter to clone current block level (para) element. What about configurable behaviors or templates that insert XML fragments Emmet style? I have been looking at ways to declare editorial aspects (things that should happen with common editorial operations like douple enter, selection, copy/paste), perhaps using RelaxNG annotations or LESS style CSS extensions. New chapters, tables and links might come with considerable package which is not evident from the schema (nor could it be).<p>I try to take a close look later...<p>BTW: What license are you using? I did not find any mention in the Github repo.