I find that if my "Replace with:" text contains escapes such as \t or \n, those strings show up in the replacement text as t and n, resp. The only way I have found to get a tab or a newline into the replacement text is to put them into the clipboard and then paste those literal tab and newline characters into the "Replace with:" field. This is very tedious. Interestingly enough, the next time the Replace Text dialog is activated, those literal tab and newline characters have been replaced with \\t and \\n, resp. Naturally, if I use these escape, it yields \t and \n in the resulting replacement.