I am not able to see any "SYS" indexes script, but am able to see other indexes script in the schema browser. My user have full DBA privileges.
If you are not able to see any "SYS" indexes script, but are able to see other indexes, then this is be design. The indexes that begins with "SYS" were created automatically by Oracle when a primary key or unique key constraint was created. TOAD does not display those. In fact in earlier version of Toad 8.0 where this information was displayed, it was consider a Bug and had to be remove. Any version of Toad after that doesn't display the script for "SYS" indexes.