Allows you to change the font size of the visual editor
Visual Editor Font Size allows you to change the font in the visual editor write field.
Once you install a plugin, you will be able to increase and decrease the font size via a
box on the write screen.
This setting doesn’t affect the font size your users will see. It affects only you.
visual-editor-font-size
folder to /wp-content/plugins/
Plugins
menu in WordPress