Use the Document Outline window to view the hierarchy of report items in a report. Tablix data regions display all the text boxes and other report items that are contained in Tablix cells. When you select a report item on the design surface, the corresponding report item is selected in the Document Outline window. Use this view to locate report items on the design surface. For example, when you preview a report with expression errors, the Output window displays a message for each error. The message includes the name of the text box that contains the expression with the error. You can click the name of the text box in the Document Outline window, see it selected on the design surface, and view the expression that contained the error.
If the Document Outline window is not visible, on the View menu, click Other Windows, and then click Document Outline.