The LearnDash Ratings, Reviews and Feedback plugin is a third-party plugin by WisdmLabs which adds, among other things, the ability to create surveys which your students can fill out to give feedback on your LearnDash courses. When you use the plugin to create a survey and assign it to a course, it will add a "Submit Survey" button to the LearnDash course progress bar, like so: 

Divi LearnDash Kit improves compatibility between Divi and LearnDash by adding new Divi modules which let you easily insert LearnDash components into your Divi Builder pages. One of the modules it adds is the LearnDash Course Survey Button module, which corresponds to this "Submit Survey" button. You can use this to place a survey button anywhere in your Divi Builder layout, and configure / style it using the module's settings.

To add the LearnDash Course Survey Button module to your page, first select the "LearnDash Modules" item from the Insert Module menu:

Then select "LearnDash Course Survey Button":

Then configure the button text, select your course and style the button using the options in the LearnDash Course Survey Button settings menu, e.g.:

Save the page, and view on the front-end and you should now see your survey button displayed in your Divi Builder layout, for example:

The LearnDash Course Survey Button module is available in Divi LearnDash Kit v1.6.1 upwards, and requires the LearnDash Ratings, Reviews and Feedback plugin.