Are you tired of switching between the Master, Web and Core database while developing?!
You can easily add a new Content Editor application (or actually an application shortcut pointing at the Core or Web database) displaying the items from Core or Web, respectively.
How to do that?
Open the Content Editor at the Core database. Navigate to “/Sitecore/content/Documents and Settings/All Users/Start menu/Left”. Create an item based on the “Application shortcut” template (or copying the existing “Content Editor” item).
You should use the “Parameters” field to manage from which database (Web or Core) the Content Editor displays the content.
(Remember to change/add values that clearly specify which database the current Content Editor displays. It’s also a good idea to setup the security settings for the new Content Editors, so it’s only the administrator/developer accessing the new Content Editors)