I have experimented with the new beta editor on my iPhone, and I have these suggestions for improvement.
There should be a three-way switch, not just a two-way switch: a) Split Screen, b) Full-Screen Code Editor, and c) Full-Screen Markdown Viewer. And the keyboard should disappear in Full-Screen Markdown Viewer mode.
It would be nice to have a View/Edit Mode button so that we would have to go into edit mode deliberately before making changes.
These feature requests suggest several configuration options.
View/Edit Button On/Off: (i.e. user can choose to use the View/Edit button or not). If the user chooses to use it, the editor defaults to View mode. If the user chooses not to use it, the editor defaults to Edit mode.
Default Initial Note Screen: could be Split Screen, Full-Screen Code Editor, or Full-Screen Markdown Viewer.
Available Note Screens: user could choose to have available one or more or all of the three screens.