For a blog module that I am developing I wanted to create an custom item editor. As you might know those are the “tabs” in the Content Editor.
1. Create a aspx file for the item editor user interface.
2. Select the core database in the desktop mode
3. Open the Content Editor and go to the following path /Sitecore/Content/Applications/Content Editor/Editors/Items.
4. You can create an item editor using the /Sitecore Client/Content Editor/Editor data template.
5. You can give your item editor a name using the header field in the data section.
6. In the icon field you can enter a path to the icon.
7. In the url field you need to fill in the url to the aspx file created in step 1
8. Save the item.
9. Switch back to the master database.