Decoys are included in the list of possible choices. Typically they don't belong to the text. The settings section has an entry which points at a decoy file which is actually a text file. Any text file can be a decoy source.
For instance a decoy file can be made up of link words, after filtering out link-words, choose the option with 4 decoys in 5 choices : TeXT Handler will prompt the right solution mixed with 4 decoys in random order.