I love the writing experience notion provides. A WYSIWYG editor page in 'zen' mode will truly help the writing experience here and the user would not need to toggle between editor and the "preview" tab to see how the post is coming along.

Some other features like

• pasting images will upload it.
• auto preview embeds when the user pastes a link. I currently do struggle with the embeds in this editor sometimes.
• word count indicator