While I understand the usefulness of the double panel layout view, for me it means one click too many in simply editing notes.
So, if possible, let a user choose in the preferences which layouts he/she actually uses. Obviously, I would deselect the double panel layout view 
Adding a WYSIWYG editor would also be welcome
And why not hide the formatting options in the read-only panel...
There is a panel toggle on the upper bar which toggles between single and double panel layouts. I’m on mobile now so I can’t send a screenshot, so let me know if you can’t find it and I’ll grab a computer.
Yes, three layouts. Of which I want to avoid the double panel one
I misunderstood the request, my bad.
It makes a good Hacktoberfest feature, so I’ve added it there: https://github.com/laurent22/joplin/issues/1900