Hi,
the wiki page contains some information about the lexer and the index /sets information.
http://wiki.codeblocks.org/index.php?title=Creating_a_custom_lexer_for_Code::Blocks_editor
This tells us which indices are valid and what each one represents:
Index 0, "Primary keywords and identifiers"
Index 1, "Secondary keywords and identifiers"
Index 2, "Documentation comment keywords"
(notice that index "3" is not used)
Index 4, "Global classes and typedefs"
In the menu Settings->Editor->Code completion you can specify the additional key word sets to be included!