Offtopic, but if you’d like an elegant hybrid† Markdown viewing/editing experience, I’d suggest https://typora.io/, another nicely-polished low-memory-consumption native app.

† I don’t know what to call this editing paradigm. It’s somewhere between source-editing and WYSIWYG. Document markup nodes are rendered as their source syntax when your cursor is “inside” them, allowing for plaintext modification of the syntax; but then, when your cursor leaves a node, it switches to rendering as its formatted output instead. You can cursor back into the node to edit it more at any time. It’s pretty unique. It’s the editing style that Slack’s new input box wishes it had.