Here’s a quick tip on how to open the Divi Fullwidth Header module’s first button (Button #1) in a new tab.

Navigate to the Divi Theme Options screen and then choose the Integration tab and add the following code to the <head> section:

Now make sure you’ve enabled the header code section by toggling the Enable Header Code button to on. This is a bit of a mystery to me as mine says Enable and if I switch to Disable, it doesn’t work. In my mind you need to click Enable to enable but obviously not. If the button doesn’t open the link in a new tab, replace all the inverted commas and quotation marks in the code above.
This post in a slight variation on the post Open Divi call to action in a new tab by divithemeexamples.com.