Ability to assign "default assigned" for ideas portals

This is actually under the Product settings rather than Account settings. From Settings -> Product -> Configure ideas, you will see an option to set the Default idea assignee.

For further clarification, IU was looking under Account>Customizations>Configure idea portals> (and then I looked through Settings, SSO, Portal Branding, Email branding, Terminology, Portal Users

@Ron Where does this exist? I am unable to locate where you can assign an idea portals review  to a particular person. 

Just so we all are talking about the same thing, the outcome here is that when a customer submits an idea for a particular product, the person assigned as the idea "owner" of that product would get notified/assigned to reviewing the idea.Correct?

This is possible by going to Product settings -> Configure ideas. From this page, you can select the Default idea assignee at the product level.