Microsoft Word already has view-only and review modes, for when you want to look at a document without making changes, but not everyone knows about those options. Microsoft is now testing a more visible switch for different modes.

Microsoft is experimenting with a new button in Word, located at the top-right corner of the window, that allows you to easily switch between three modes --- Editing, Reviewing (for suggesting changes and adding comments), and Viewing (a view-only option). Those options already exist in Word, but they are located in different menus that might be difficult to find.

Mode switcher interface in Word
Microsoft

The name of the new button also changes depending on what mode you're using. That means it's always easy to tell what mode you're in: just look at the top right corner. It's worth noting that Office Online has had an identical button for a while, but located in a slightly different place (at the end of the ribbon tabs).

Editing mode screenshot in Office Online
Word Online

Microsoft says the new button is available in the Beta Channel of Microsoft Office, starting with version 2206 (build 15314.10000). It should appear in the regular stable builds of Word sometime in the coming weeks or months, assuming no significant bugs show up in the testing process.

Source: Office Insider Blog