Markdown has built-in syntax for the quote blocks

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> Quote block, quote block, quote block, quote block ...

which are rendered in the special way

I recently had the need for Side Note block in this post, but I had to workaround it using existing Markdown capabilities, and I’m not quite satisfied how it looks.

Is it possible to extend Markdown syntax somehow to have similar (special way rendered) “Side Note” blocks that could look (roughly) like

?

Key features are:

• Block could have “Side Note” title to avoid confusing it with Quote block.
• Collapsed by default to show only few lines of content (like Code blocks).
• Some margin at the left probably (to make it more “side”).

Personally, I feel that all (or almost all) markdown features may need to be supported in the Side Note block content (including images, code-blocks, lists, tables, quote blocks). However, I don’t think that I will ever need nested Side Note blocks.