Some of the default notification emails have quite a lot of text included, so full-screen mode is quite significant. 

Also, depending on your screen size, you may find it difficult to view the entire email template when making required edits:

• Once the required email template has been selected, click the 'Full-screen' icon above the template itself:

For further information on other options available, please refer to the following article:

• How can I edit my Email Templates?