I am trying to make two indexes: one - for subjects and the second - the author's index.
Is it possible to do it in ID?
I do this every month by adding a key character (or string) to one type of entry, but not the other.
For instance, index your subjects just as you do now.
Index your authors as ~Jones, Tom; ~Smith, Bob; etc
When you create the index, all the "~" entries will be grouped so you can easily "extract" them from the main index.
HTH
AG