ReplaceWithSpecial takes a dictionary/mapping that you can configure in the Settings tab and generates all possible ways a field might be written with each mapped character(s) being replaced with its mapping.
You can also use this option to attempt to guess intentional misspells a user might make by replacing 1 or more characters.
caution
This is a powerful but dangerous option for strings. The danger is that when used with large permutations it can "explode" the wordlists as for each possible replacement(s) of characters there will be one variation of the field generated, meaning 1 more word per permutation.
