Tracking workflow changes done at design time

Design time changes are signaled by using the IComponentChangeService .Net interface. The host needs to provide this service through the hosting site. You can then add handlers to the events defined on this interface to process the events you're interested in. (look into MSDN for more information)
IComponentChangeService provides an interface that can be used to indicate the methods that handle the following events:

*ComponentAdded , raised when a component is added.
*ComponentAdding , raised when a component is about to be added.
*ComponentChanged , raised when a component is changed.
*ComponentChanging , raised when a component is about to be changed.
*ComponentRemoved , raised when a component is removed.
*ComponentRemoving , raised when a component is about to be removed.
*ComponentRename , raised when a component is renamed.
ActivityChangedEventArgs is the parameter that's passed to the virtual function OnActivityChanged defined on the ActivityDesigner class. If you write your own designer that inherits from ActivityDesigner , you can override this function and be called with the activity associated with this designer changes. It is not a place where you would record all changes happened in the designer.
Shelly