When you come across a string that you'd like to change without getting your hands messy with code / child theme / po / mo files, you can use a simple plugin called "Say What?" https://wordpress.org/plugins/say-what

To use this plugin you need the original English string and the text domain.

The text domain for the Divi theme strings is: Divi
For the Divi Builder: et_builder
And for the Extra theme is: extra

Let's take this example: 

Our posts have a comments section and we want to change the "Submit a Comment" string of the Divi Comments module to something else.

The original English is: Submit a Comment, and the text domain is: Divi because it's not generated by Divi Builder (it's part of the theme).

So go to Dashboard => Tools => Text changes: 

Click the Add New button and fill-in the info like so:
​

And the results are: 

NOTE:
​
If you are confused by the text domain, just use all 3 suggestions.. Divi (for the theme), et_builder (for the strings generated by the builder) or extra (for the strings generated by the Extra theme).
​
One of those will surely work! :)