There are many ways how to make copies of objects. I recommend you to have a look at the Help file, Index tab and please type ‘copy’ - select the ‘copy entities’ topic.
To make a copy in Model Explorer (ME), select the entity, press CTRL and drag it to Entities folder name and drop it there.
Flash movie on copying and moving entities:
Use case - template entity: Feel free to create such entity in your model (e.g. via Model Explorer). The entity will exist in your model but doesn’t have to be in any workspace (the Shortcuts folder of the entity in ME will be empty.) You will make copies of the template entity and will display the copies on workspaces. Do NOT forget to edit the template entity (e.g. via Model Explorer) and clear the Generate checkbox on tab General. The entity will not be generated in DDL script then.
If you have more questions, please write me back. Thanks.