- save your project in a .sbproj file
- keep the project open in Model Builder or load it if you have already closed it
- In the toolstrip menu of Model Builder, choose 'Model' → 'Load Model from file', select your sbproj file
- Choose the model to duplicate in the model list. SimBiology will add the model to your project after adding '_1' to the name since a model with the same name already exists in the project