[Quoth]

You can have a first-paragraph-is-scene break style in the MS Word or LO Writer with no first line indent and as much top margin space as you iike.

Or a scene-break style that has top, & bottom margins and is centered with 0 for left and right margin and put one of
. . .
* * *
~
-
–
—

etc. in that scene break paragraph.

There is no need ever in an ebook (or source wordprocessor file) to use directly entered empty lines, extra spaces or tabs. Not even for paper print. It's only for an MSS typed on a physical mechanical typewriter. Obsoleted 40+ years ago.

Anything deliberately at the top of a page (like a heading that forces a new page) is better with padding-top as margin-top is often ignored for the first element on a new page. Web sites don't have pages like ebooks, except on the Print option.