The GT3 Gallery Pro has the custom module for DIVI builder.
You can add the photo gallery in the next way.
1. Please create a gallery using the GT3 Gallery custom post type. You can see how to do that here https://gt3wpgallery.com/kb/docs/what-is-gt3-galleries-custom-post-type/
2. Create a new page or post using DIVI. Once it’s done, please add new element, in the search form please type “gt3” you will see our gallery module, please add it.
3. In the gallery module, please select the existing photo gallery from the list. That’s all.