]
Means LAST or End Class (in Regexp)
Right bracket (]) is short for the LAST line in the file, by default. This abbreviation can be changed with Set Zip.
/delete ] {delete last line}
In the documentation, [ and ] indicate optional syntax fields (e.g., Delete [rangelist]).
Right square bracket (]) in regular expressions indicates the end of a character class.
/List "x[abc]z" {character class ends with “c”}