Ok, I think I got a working solution.
1. copy all objects from the Layout to the new Project-Layout (it seems as if I can only copy&paste from within Layouts)
2. Create the needed Families manually
3. Add any other object-types, like Touch e.g. wich are not associated directly to any visible objects
4. In the Eventsheet from the new project, create a temporary comment and select it.
5. copy & paste first all the global variables, since, they are referenced in the conditions. You can only paste, when you've got something other selected, thus the need for selecting the added comment.
6. move the comment to the bottom and now copy & paste the other conditions, groups, like before.
Works, good enough for me right now. If anybody knows of a more streamlined way, please feel free to explain.