News Courtesy of cPanel.com:
This post was originally added to our blog on Aug 18th, 2016. It has been updated for accuracy, and readability.
In the blog post “Managing Multiple Domains from a Single Hosting Account,” we explain how to manage different domains you may own in a single cPanel hosting account. There may be certain circumstances or occasions where you will want to split off an addon domain into its own cPanel account. In the following blog post, we will show you exactly how to accomplish this! Users with root-level access or resellers with the “Rearrange Accounts” Privilege will have access to move an addon domain into its own separate cPanel account. So let’s get started!
Ryan’s Take 
I was actually unaware of this feature. cPanel’s Web Hosting Manager is a fantastic option for easily managing hosting accounts on your server. Creating a primary domain and then adding addon domains to that account allows you to organize and structure websites in groups with shared attributes. The most useful feature that I find by doing this is to have a staging domain to share with your clients before a site launches.
For instance, a typically preview link might look like this: http://hoststagingdomain.com/clientwebsite.com. You can have a client review their new website without having it live. If any changes are needed, they can be completed without potential customers and visitors experiencing any embarrassing edits for that business. Then, when the site is ready to launch, it is simply a matter of replacing that domain string (http://hoststagingdomain.com/clientwebsite.com) with (http://clientwebsite.com) in the MYSQL database. This can be done with a WordPress plugin or exporting the database and using a file editor to replace the string on each occurrence.
Once the URL has been replaced entirely, you need only to edit the DNS records of the desired domain to point to your server. One thing I learned the hard way with addon domains is that it is a good idea to block them in the primary account’s robots.txt. I found that even though I wasn’t promoting preview links online, Google still managed to index some websites that hadn’t been launched yet. Having http://hoststagingdomain.com/clientwebsite.com and then all the pages under it indexed is a huge problem. Trying to remove and clean up the indexed pages is time-consuming and could pose duplicate content issues once the site does go live. Creating a block in robots.txt forces search engines not to list these preview links, no matter how they are discovered.
So why would you want to move an addon domain into its own account anyways? Perhaps a website is growing at a rapid pace, moving it will make it easier to manage server resources and change settings without affecting sibling addon domains. Or maybe you want to assign a domain a dedicated IP address for one reason or another. I wish I had known about this feature a couple years ago. It would have come in handy when I needed to move some of my bigger accounts!
