To run this script
Select Script → Data → Delete_Unused_Datafiles from the Menus.
Or in Version 13 or higher you can run the utility directly from this page using this button.
This script will go through a project to find which data files are used and which are not. Used is defined as being used as a subcircuit in a schematic or any soft of measurement on the data file. It will only search for port parameter (touchstone) files, MDIF or Generalized MDIF data files. After it has found all the unused data files, it will present them in a list and ask if you want to remove them, add an underscore to their name, or do nothing. For the underscore, these data files will sort to the top so you could manual remove them later if you wanted to.