I was so crushed to see that this is an Electron app. I'm a longtime iA Writer craving built-in Pandoc export, and this is basically my dream app. I just can't get behind running all of Chromium to support a minimalist text editor.
1. I think writing-focused Markdown editors should not feel obligated to render arbitrary HTML in their previews. The format may support it, but the editor doesn't need to—one of the great things about Markdown is that your editor can be anything from vi to VSCode.
2. On the Mac, there is an extremely easy API to display a WebView (WKWebView), which would cut the size of this executable to roughly 1/100th of its current size, drop the memory usage, and reduce energy consumption. You can even keep most of the business logic in JavaScript if you want.