Individual models (systems) in a project can be exported as .mechdat files, which can be transferred from one WB project to another. To export the mechdat file, open Mechanical from the system you would like to move (e.g., M1), go to File > Export. This will create the mechdat file for that particular system, you can import this into any open WB project, go to File > Import and select the mechdat file created in the previous step.