> For markdown hiding, we are still searching a good UI/UX solution.
Have you tried FoldingText? It hides all Markdown until the cursor is over the affected text. I think it's a lot more elegant than an edit/preview model since for most people reading and editing are continuous and intertwined.
I have FT, and while I don't use it regularly, I have kept up with with it through its long revision process. If you search around you can find plenty of reviews that will give you a better overview of its features and so on than I can here.
But, as for my personal opinion of the app, I think that at its current discounted price the app is worth the cost if you specifically need an outliner/planning app. I think that the biggest problem with FT is that if fits a weird niche: true, the interface is easy-ish to use, and offers quite a few nice amenities (e.g., focusing, quick navigation), but I don't know that these features alone make it worth the original price. The 'power' features it includes—scripting, plugins, and all that—are interesting, and others may find those more useful than I do, but I suspect that most people who will be interested in the deep features will already be using effective, powerful alternatives. This is certainly the case for me, as I use Vim + plugins (Vimwiki, Notes) to replicate much of FT's basic feature-set, and nValt (or Notational Velocity) to cover the basic note-taking aspect. While I like the nice interface of FT, for me it doesn't offset the annoyance of needing to load up a dedicated app every time I want to outline something, especially when I can use Vim for all of my plaintext projects. Ultimately, I think it is an interesting idea that is nicely implemented, but every time I try to do something with it I find that my other (free!) tools do the job with less fuss.
But, YMMV, and you might try downloading the trial version just to see how the app works: http://www.foldingtext.com