I don't know what to make of this. I like the general idea but I really don't like the use of Markdown here.

Markdown makes writing markup faster and reading markup easier. It's a limited set of syntax elements optimised for writing and reading text. No more, no less. It is not, however, a new set of language elements to be used for whatever purpose.

For example, how is this:

  __Basic Button|Icon：User,Text：Add Friend__ 

Any better than this?

  <button icon="user" text="Add Friend">

Even YAML seems to be much better suited for structured data like this.

  button
      icon: text
      text: Add Friend

If your aim really is to "lessen the cognitive load", why not work with tools that better work towards that goal?