The mentioned Bear and Typora solve this by showing you the "raw" Markdown at least when your cursor is there. So anytime you edit, you're editing in text, as you mention. But you don't need a second "display" panel to do that.
Both tools do it differently. Typora shows it when your cursor is there, but otherwise hides the Markdown. Bear always shows the Markdown but applies the corresponding style to it.
Both tools do it differently. Typora shows it when your cursor is there, but otherwise hides the Markdown. Bear always shows the Markdown but applies the corresponding style to it.