It is very time consuming and uncomfortable to maintain the structure in the content pane when adding a CAD file. A CAD file is compose multiple features like Annotations, Multipatches, Points, Polygons and Polylines. And when adding the file, all features spread all over the content pane instead of group themselves by default. In ArcMap, when you add a CAD file, all features are group by default making it easier to organized all layers in the content pane or if you want to delete all CAD features from the same file. Please add GROUP option inside the Project / Options / CAD when adding a CAD file to the content pane.