[hysan]

Toggleable tree view for navigating, opening, closing, creating, and deleting files. You also mentioned previewing, but it'd be nice if you could have toggleable split screen mode for live previews (or wysiwyg mode). Last would be a way for contributors to write extensions to add additional features.

[fizzbucket]

Got the split screen live preview already; tree view sounds a very useful addition, though.

Extensions are also a good plan; the interesting thing is that many of them end up being routed to pandoc, so they can be done with document metadata in any case. For others, one easy thing to do might be to rewrite some of the bits in C++ in PyQt, then have the possibility of importing classes that inherit from the originals and override functions. Does that make sense, do you think?

[hysan]

I've never written any software that had an extension system so I can't comment on whether or not it's a good design. My guess is that so long as the system is well documented, then it can work. Hopefully someone better qualified can address this.