I have found this command *typeset* and the option * -f *, which should provide me the list of all the currently defined functions. Is there any possibility of specifying the file in which this command to search [or it looks only in the current shell script] ?
It does not look in any files at all. The ksh process is displaying stuff that it has stored in memory. You can type a function into your interactive shell and later use typeset -f to see it, (assuming nolog is off).