Off to the right of the current page (the Permissions tab), there is a "Show more available" permissions link. There are some items in there that we would like to configure, so click that link and it will show several more permissions that we can set.
We've already turned off all subdomains elsewhere, so there is no reason for this to be turned on - except, perhaps to confuse your customer. This should be turned off unless you have allowed subdomains earlier.
Domain aliases management
We are allowing domain aliases on this subscription. For some reason, Parallels considers a domain alias to be an advanced concept, but we would like to allow our customers to use them anyway. This option should be turned on.
Additional FTP accounts management
This option either allows or prevents users from creating their own secondary FTP accounts. Most web hosts will leave this turned on so the user doesn't have to give out their panel password to their web developer. However, any new account is a potential security risk, so if you know you won't need them you can turn them off. For our purposes, we will leave this option turned on.
Ability to change mail settings
Users normally have the ability to change the webmail client they use or to configure how non-existent email addresses are handled by the mail server for their domain. If you have a need to enforce a single configuration, you can turn this option off; however, most web hosts will leave it on. We will leave this option turned on for now.
Mailing lists management
Plesk allows users to manage their own mailing lists, including users on them. We have turned off mailing lists already, though, so this option may only serve to confuse a customer. You should turn it off here unless you left mailing lists turned on.
Access to advanced operations: Website Copying and Website Maintenance Mode
Plesk has the ability to copy entire websites to or from a domain, either locally of via FTP. This is a very handy feature that makes simple backups and website transfers a breeze - if there are no complications, which there frequently are. You may want to turn this off for support or security reasons, but the Maintenance Mode feature may make the option worth leaving on. We'll leave it turned on here.
Password-protected directories management
Sometimes a website will need to password protect a directory so that the general public cannot view its contents. Plesk allows you to manage directories and any users along with their passwords that are allowed to authenticate to view it. This is a very handy feature that most web hosts have, so you should leave it turned on.
Ability to manage auxiliary user accounts
Most customers would like to be able to allow their web developer (or their secretary, or their accountant) to make changes to their web hosting without giving out their password or allowing them to change things they should not be changing. Plesk allows these customers to define access roles and assign auxiliary accounts to those roles, which makes limiting access much more easily accomplished. This is a feature not found in many other control panels, and it is a very large security benefit for your customers. You should leave this option turned on.