This mailing list is for FreeSWITCH, you ask questions about FusionPBX in IRC channel #fusionpbx
That said, you can find all scripts in /usr/local/freeswitch/scripts. Also, what you are trying will not work, FusionPBX will not write config files on filesystem.
I have tried to disable lua and enable xml generation on fusionpbx, but it didn't worked at all, files xml were not generated and configs were not loaded.
How can I find the source code for xml_handler (lua source code), defined bellow?