If you add "<br/>" (the line break tag) to the list of allowed HTML tags $allowedHtmlTags in classes/core/String.inc.php around line 240, you'll be able to use this tag in articles. Let me know if you have any trouble. This is definitely the easiest solution, although not as clean as the ideal solution, which would be to add a subtitle metadata field. FYI, we'll be making metadata set changes easier in a future release.
Open Journal Systems Team
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