UIMap Toolbox allows you to restructure, split and merge UIMaps created for Microsoft CodedUI tests in Visual Studio 2010 and 2012. Developed in C#/.NET 4.0
User Guide including some thoughts on developing maintainable CodedUI tests can be found on the Documentation page.
Integrates into Visual Studio, so it's possible to open UIMap Toolbox directly from the Solution Explorer window:
UIMap Toolbox with two UIMaps opened: