You can drag and drop to move or add project files. Drag files in the Simulink® Project to move files within your project. You can drag and drop files from a file browser or the Current Folder browser onto the All Files or Project Files view. If you drop a file in the Project Files view, you add the file to the project.
If you drag a file from outside the project root, this copies the file into your project. If you drag a file within project root, you move the file.
See also Add Files to the Project.