This request had been accepted for the development of d7.1.3 ( if I remember correctly ) . But I see that at the time was delayed ( d7.3 ). These links can help:
http://www.boonex.com/trac/dolphin/ticket/3104
http://www.boonex.com/forums/topic/Add-Row-for-Page-Builder.htm
http://www.boonex.com/trac/dolphin/ticket/3104
http://www.boonex.com/forums/topic/Add-Row-for-Page-Builder.htm