To Merge Part List Rows (AutoCAD Mechanical Toolset)
In the drawing area, double-click the parts list. The Parts List dialog box is displayed.
With the CTRL key pressed, click the row heading of the rows to merge. The program selects the rows.
On the toolbar of the Parts List dialog box, click . All selected rows are merged into one item.
Note: You can merge only rows containing the same part. You can merge parts from external reference (xref) drawings only with parts from the same drawing. You cannot merge them with the same part from the host drawing or with the same part from other xref drawings.