If you wish to divide a large model into several workspaces (WS), first create a new workspace and then select objects that should be displayed in the WS. This macro offers you an alternative method. Select various objects (Entities, Views, Materialized Views) in the Model Explorer or Object Viewer, right-click any of them and select Add To New Workspace option. New WS is crated and objects are added in there.
How to install custom packages: