kameleonosis

Visual Tools adds a customizable control panel for admins to apply global visual changes — such as font size, spacing, background and text color — across the entire website.

visual-tools-front-end-panel

Provides global visual customization (font size, spacing, colors) for WordPress admins, with live preview.

Nikolay Bachiyski

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

Allows you to change the font size of the visual editor

visual-tools-front-end-panel vs Visual Editor Font Size