trondåge, for your first question, I would recommend that you create a new section and assign it to the secret folder(s). Then view the permissions for <i>Anonymous</i> users, which is under <i>Users > Roles</i> to make sure they do not have any rights to read or change that section. You may need to change the permissions under the <i>Section</i> box to highlight only what you want them to see, making sure that <i>Any</i> is no longer selected. Sections are ideal for hiding content from a group(s) of users.
Concerning your second question, yes you can add an item in the left menu in the admin section. Take a look at the templates under <i>design/admin/templates</i>. You may need to look around a bit to find the right file, though it would be faster to turn on debug under <i>[TemplateSettings]</i> in your <i>site.ini.append</i> which will show you every template used to display the page. Then just insert the code or link you want displayed there as you would with any other template.
Hope this helps,
Alex
Alex
[ bald_technologist on the IRC channel (irc.freenode.net): #eZpublish ]
For suppressing folders in the normal view, you may also copy the folder class to a new class and create folders with the copied class. You can easily change the anonymous user role to only display the folders you want. This may be better in case you mix normal filders with "folders to be hidden". If its only a certain tree(s) you should suppress, sections are the way to go.