Flat, Clean and Group DWG files in 3dsMax
Clean , Flat and Group DWG files: This Macro Script allow the user to Flat, Clean empty layers and Group DWG files when imported into 3ds max. This plugin could be useful for architects that want to work with DWG information as reference and want to remove anything that is not important. Also, this plugin will Flat your DWG files in case they comes with some errors in Z axis.
Does not work on newer versions of 3ds Max
You can try this one:
https://cgtricks.com/copy-paste-dwg-useful-3dsmax-script/