In the project-list, select the document set you want to copy. Drag the document set onto a project and release the mouse button to drop. A copy of the document set including the documents will be created in the destination project.

In the project-list, select document type you want to move. Drag onto a project or document type and press Ctrl key (notice the change in icon); while holding the CTRL key release the mouse button to drop. The files and their document records will be moved to appropriate document type in the destination project.