If a legacy add-in exists, specifies the dll of the legacy addin. If a full path isn't specified, Visual Studio will look ...

If a legacy add-in exists, specifies the dll of the legacy addin. If a full path isn't specified, Visual Studio will look in the visualizer directory next to the .natvis file that specified the add-in. A regular display string is still allowed in conjunction with an add-in, and will be used as a fallback if the add-in dll cannot be loaded.