Risolto! in questo si ho trovato la soluzione usando il pacchetto splintindex.
Basta solo riadattare il procedimento per il proprio editor…
http://wiki.lyx.org/Tips/Indexing
With other classes, the splitindex package can be used. For example, we want to have an additional “Index of Names”:
Make sure the splitindex package is installed
Change Preferences -> Outputs -> LaTeX -> External applications -> Index command to splitindex -m ‘makeindex -c -q’ (if you use different makeindex options or xindy, you can adjust the command accordingly, for instance splitindex -m ‘texindy -L german-duden -M book-order’ works as well).
In your preamble (Document -> Settings -> LaTeX preamble), insert the following code:
\usepackage{splitidx}
\newindex[\indexname]{idx}
\newindex[Index of Names]{nom}
Insert the Entries to the main index as usual (Insert>Index Entry), and insert the index itself as usual (Insert>Lists & TOC>Index List).
As for the second index, add in TeX mode at the place where the index shall be printed: \printindex[nom]
Insert the entries that should go to the Index of names in TeX mode: \sindex[nom]{Knuth, Donald E.}