I can't do it...
From MSDN "Create a Maintenance Plan (Maintenance Plan Design Surface)", I found this:
To create a maintenance plan
1.In Object Explorer, click the plus sign to expand the server where you want to create a maintenance plan.
2.Click the plus sign to expand the Management folder.
I can't find the "Management folder", but surely it seems to be applicable for SQL 2012 (I have SQL server 2008 R2). Is there something similar for 2008 R2?
BTW, I reset the "database" list by doing a backup with the option "Back up to new media set and erase all existing backup sets", and the list from "Tasks\Restore\Database" (in Management Studio) is only one line (wich is what I am looking for but for the "restore files and filegroups" wich is not reset even if I do a "file and filegroups" backup...?)