Currently it isn't possible to re-import existing project. Re-importing isn't easy task because a lot of different changes in the model and in code can happen, which would need to have completely full gui to determine which changes are the latest.
Imagine the situation when you update entity in the model and in the code. After that it would be necessary to tell the application which change is required. Because of this we currently don't have ability to re-import model.
We have some ideas how to implement it in the future but I can't promise specific date right now.