As the reach of the robot is same in both versions, so the same RSLIB file is provided for both of them.
If you still wish to take the exact RSLIB file then you just update your Librarytypes.xml file in
“C:Program FilesABB Industrial ITRobotics ITRobotStudio 5.11ABB LibraryRobots”
folder. It’ll still bring the same model but will make a system for 45Kg version.