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:
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! :)