In this article I will talk about how to properly change the “Thank you message” in the Contact Form Module in Divi 2.5.6. For this you will have to use or to create and activate a child theme for Divi.
The long answer: Starting with Divi 2.4, the Elegant Themes, brings a new way of working with your theme. Basically they introduce new features, which you only see in premium plugins like visual composer but the problem with those kind of plugins, is that sometimes they look much better in back-end then in front-end.
The Front-end Editor lets you create your pages from the front-end of your site. You no longer have to navigate to the back-end, create a page that you’re not sure how it’s going to look on your site, preview it before you publish, and then publish.