The Share Access option allows you to retain control of the domain while granting your customers or co-workers access just to certain domain editing features.
The domain will show up in another account with limited modification options.
Keep in mind that this option doesn't work for the SSL service, and there's no way to manage the SSL certificates from the other user account.
Check out this KB article on how to share access with another Namecheap user.
That's it!
If you have any questions, feel free to contact our Support Team.