When setting up the system security, I put an user into portals administrators g

Tried the same on 6.6.1 and 6.7. The user was able to view the System tab. Which version of Appian are you on?

I can view the system tab but I cannot update the Primary Navigation.

Primary Navigation is to control how can see the system tab. I can see the System Tab when I am member of Portal Administrators. Is member of Portal Administrators can update Primary Navigation setup?

Please note that my version is 6.7.1

I tried to to update the Primary Navigation as a basic user who is a member of the Portal Administration Group, but encountered an error. On checking the application-server.log, found an exception that says "User Does Not Have Rights to Perform this Operation". So, it does look like only Sys Admins can make changes to Primary Navigation. Here are couple of links that might be useful to understand this further - forum.appian.com/.../System_Administration_Security
forum.appian.com/.../System_Administration_Pages

This is exactly my case. I need to confirm if Appian designs that only system administrator can do it. From the link forum.appian.com/.../System_Administration_Security, Portal Administrators should have the right to change the information in System Tab. But it is not I expected.