Well, I have no idea what exactly IBM Case Manager is or what its toolkit can do. However, if you have a system in which you have made manual changes to a source code in your development environment, it is usually a good idea to make such changes with as few manual interventions as possible in other environments such as "test" or "production" implement and reproducibly and in one step.
So, if I understand you correctly, your idea of "Make script changes with Case Builder" includes manually re-entering the changes you have already entered in the development environment? That sounds pretty prone to error and even if you change only a few statements, I would avoid such an approach if possible. Better find a way of automate The approach you sketched first: "Export from developer and import in test" – It probably will not be the last time you have to do this.