That would be cool, but no, nothing like that exist. But you could make it yourself.
The Portfolio layouts are called Navigators and they are written in flash. You can download the Navigator SDK for free and write your own. However, Navigators are sandboxed. They do not have direct access to the documents. The SDK provides some specific information, including access to what's called the file metadata. These are the data fields displayed in List view. The field values are defined and filled in by the creator of the portfolio, or the navigatore. Actually, document level javascript in the cover PDF can create and fill out these fields. So you could create a navigator that would work in conjunction with a document level JavaScript. The script would collect the bookmarks from the embedded documents and report them to the metadata that the navigator could then display.
Alternatively, I created an Acrobat plug-in that copies embedded file bookmarks into the bookmarks on the cover PDF. So at least that puts them in one place, at the top level. But it's not free.
You'll find it Here: pdfscripting.com plug-ins
Thom Parker
The source for PDF Scripting Info pdfscripting.com
The Acrobat JavaScript Reference, Use it Early and Often
The most important JavaScript Development tool in Acrobat
The Console Window (Video tutorial)
The Console Window(article)
Having trouble, Why Doesn't my Script Work