One of the first things that you notice when you start working with the DSL Toolkit is that you have to do the synchronization between the Domain Model Definition and the Designer Definition files (.dsldm and .dsldd respectively) MANUALLY. At this time there is no support from Microsoft for doing this automatically and it is tedious work, believe me...
But Modelisoft has created an excellent Visual Studio 2005 addin for doing this synchronization. So it is a “Must have“ tool when dealing with the DSL Toolkit
Pablo