You probably know how to use the mailto command for quickly linking to one email address. You can not only link an email address but a subject line as well. 

Just highlight the text you want to put mailto link on and click on the hyperlink icon,

In the pop-up window, type in the correct text.

The link text should be:

mailto:anna.ov@example.com?subject=Check%20out%20our%20hottest%20deals

• Use the usual mailto:  
• Then enter an email address, 
• After that add ?subject= and then follows the subject line that you chose.
• Between every word use %20 as a spacing between the words. 

Learn more about Mailto options here.