Changing Unassigned Symbols
While in the Resource Symbols dialog box, you can edit or delete existing symbols that are not already assigned to a resource or object.
To change an unassigned symbol
In the Name box, select the unassigned symbol, and click Change.
Edit the symbol's name or value in the boxes provided in the Change Symbol dialog box.
To change a symbol that is assigned to a resource or object, you must use the resource editor or Properties window. For more information, see Changing a Symbol or Symbol Name.
For information on adding resources to managed projects, please see Resources in Applications in the .NET Framework Developer's Guide. For information on manually adding resource files to managed projects, accessing resources, displaying static resources, and assigning resources strings to properties, see Walkthrough: Localizing Windows Forms and Walkthrough: Using Resources for Localization with ASP.NET.