Opening links in a new window is considered bad form in today's web as it has been abused. Yet, it still serves a purpose for demonstration sites that require more than one window open at a time. This method will work for those links that you enter into the body of a post.
After entering the link using the Quicktags button for "link", add target="_blank" to the individual*- link you want to have open in a new window when clicked. Consider adding text indicating that this link will open a new window, as required by web accessibility standards.
<a href="http://example.com/page.php" title="Page Title - opens in new window" target="_blank"> Page Title (Opens in new window)</a>
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