Rufnex

FullscreenWidth is a very simple Plugin, that adds a input field to change the editarea width, next to the toolbar buttons at the fullscreen view.
The standard width of the WordPress editarea is 647px, for some reasons this was to small for me. FullscreenWidth let you change the desired width on the fly by simply type widith in the input box. Afer you click elsewhere on the screen the width of the editarea is changed.
Note: The width is set as long you dont reload the browser.

FullscreenWidth

FullscreenWidth adds a input field to change the editarea width, next to the toolbar buttons at the fullscreen view.

Harmandeep Singh

This WordPress plugin will change the Gutenberg editor width, which will be make it easy to use Gutenberg editor.

Page Editor Full Width Option

This plugin adjust default width of the page editor.

FullscreenWidth vs Page Editor Full Width Option