The Auto-Correct feature allows you to order the program to change a word or sentence into something else on the fly, i.e. while writing it in the edit window.
Use a | (pipe character) as line break delimiter.
Example:
Replace #1 with Subtitled by|John Smith|The Subtitling Company
will give you three lines in the edit window:
Subtitled by
John Smith
The Subtitling Company
All you have to do is write 1# (or whatever you entered in the Replace field). 
You can also auto-correct a range (using the Format/range edit menu or Context window popup menu), which could be very handy with lists (custom dictionaries) of frequent words that always need to be replaced in languages that are similar (e.g. swedish to danish translation), but please consider making separate custom dictionaries for each language translation, otherwise custom dictionaries might prove difficult to maintain.
The Added Words Dialog allows you to add or delete words in your custom dictionary.
The Excluded Words dialog allows you to mark words that will always be considered incorrect.
See also: