To put one module inside another, we will first create the child module ie. the one to go inside the other one. We do this as a Beaver Builder template.
Then on our page we paste a shortcode with the URL slug into the parent module.
Copy the URL slug. It's the last part of the URL, between the /slashes/
Now go to your page to add the module to a module. In this case it's being added to the tab of a tabs module.
Use the code below:
Paste it into your module, replacing "my-post-slug" with your slug.
Here's the result: