Flandrew likes Org mode but he wanted to improve his workflow with it a bit. So he wrote some code that he called Fold and Focus—Focused Navigation. The idea was that when in Org mode a single key would move to the next or previous subtree, position that subtree at the same place on the screen, and have everything else folded so that he could concentrate on the current subtree.
That worked out pretty well but after a while wanted to bring the same sort of functionality to Elisp buffers, which he did. Recently, while working in a Markdown buffer, he automatically tried to navigate in the same way but, of course, it didn’t work. So he did the natural thing and ported focused navigation to work in Markdown buffers.
I don’t use Markdown so I have no use for this functionality but it seems like a really useful addition to your toolkit if you do. Take a look at flandrew’s posts. He has animations that show how it works in all three environments. If the project seems interesting to you, take a look at the project page.