To Externalize a Component or Folder (AutoCAD Mechanical Toolset)

Click Structure tabTools panelStructure Catalog. Find
Click the Current Drawing tab.
From the Definitions panel in the Mechanical Structure section, right-click the local component or folder you want to externalize, and select Externalize.
In the New External File dialog box, select the location the new file must be saved to.
In the File Name box, type a name for the drawing file.
If the file must be created using a specific template, select the Use Template File check box and from the drop-down list, select the template.
Click Save. A new file is created and the component is saved to it. The Definitions panel in the Mechanical Structure section indicates that the definition is an external reference.