To Import Model(s) by Dragging from a Second Session of the Product

Open the Models dialog in both sessions of AECOsim Building Designer.
Select one or more models that are to be imported.
Drag the selected models to the Models dialog in the other session of AECOsim Building Designer.
Where one or more models being imported have the same name as existing models in the open DGN file, then an alert box gives you the option of overwriting the models in the active DGN, or renaming them automatically as they are imported.