why does shell namespace extension not show in windows explorer treeview?

Question

The shell namespace extension I am working on is registered as a virtual folder junction point under MyComputer:
  Software\Microsoft\Windows\CurrentVersion\Explorer\MyComputer\Namespace\<my extension CLSID>

It shows up in folder view when I click "computer" in the windows explorer treeview. Then double click the extension icon to navigate the extension in the center, folder view panel of windows explorer.  But it never shows up in the left side treeview panel. How to enable the extension to be navigated in the left side treeview panel of windows explorer?

When I run the extension in debug mode the only method that is called when windows explorer is started is IPersistFolder::Initialize.  Not until I double click the namespace extension icon in windows explorer do I see any interface methods other than Initialize being called.

In the registry, the attributes value under the ShellFolder is set to SFGAO_FOLDER | SFGAO_HASSUBFOLDER | SFGAO_CANDELETE.

thanks,