Hi Luca,

The CAD directory is a flat directory structure so yes, it can become very cluttered.  My 2 recommendations are:

• Always save a ZAR of your system so the CAD files will be part of the ZAR.  This way you can delete everything and simply extract the ZAR when you want to re-analyze a system.
• Use the new Project Directories in the last 1-2 releases of OpticStudio.  The initial release in 21.3 includes all the files in the Objects\CAD Files directory ("Convert to Project Directory" new feature: two issues | Zemax Community).