Custom Views
A custom view is typically a read-only window control object (derived from System.Windows.Forms.Control), and is provided by an extension to represent the schema in a display format customized for the type of file or files supported by the BizTalk Editor extension. An extension can implement multiple custom views, though it need not have any custom view.
A custom view is displayed as an additional view in the same BizTalk Editor pane as the XSD view, accessible by using tabs at the bottom of the views. For example, the Flat File Extension adds a new view with a tab labeled Flat File.