You can query the Modeler database to find that information. Download the SQLite Manager add-on for Firefox and execute the following queries on the Modeler .mpr file.
SELECT COUNT(*) FROM MetaObject SELECT COUNT(*) FROM Attribute SELECT COUNT(*) FROM MF_Microflow SELECT COUNT(*) FROM MF_Activity
Note: This works in 2.x but not in 3.x projects.
I don't think this is possible the Modeler, but you could use the Object Browser module to get a rough overview.
It creates objects for all your entities, attributes and microflows, which you can easily count in a microflow. (Do note that this includes itself, but you can filter per module if needed).
Ok great I will investigate its use, looks like a good lead. Thanks