T M
I do no work in Word. My
solution 
is to work on the
block. For most part a block is what is inside a P,H# or DIV tag pair.
Margin is the thickness of the Mortar between the blocks, and can be controlled for each side.
Being a
visual thinker, I like the picture found and described in Section 8
http://www.w3.org/TR/2011/REC-CSS2-20110607/box.html
Since the Body contains a stack of many block, each with their Mortar, before the Body tag can
close, the last layer of Mortar hast to apply. If this is the Margin-Bottom, it may be the only thing on the screen (at the readers current Zoom setting). That is why I avoid using margin-bottom for most paragraphs. YMMV
Back to your scene break problem: many devices ignore
extra 'non-printing' white space.
to trick it into accepting multiple blank lines, the use of a Non-breaking space is use (
Code:
The HTML entity
) on each of those lines
I prefer to work on the code. So I create 1 or more styles for scene breaks. Now I can change my mind on how much white space to allow for each class.
IMHO working with the code is so much easier that trying to make a a Word Processor generate workable (and
cleanish) HTML