Hi Antoni 
First, note that I just realized that the page breaks are only being ignored when enclosed at the begining of a paragraph to which a style is assigned. For any “no style” paragraph, the page break behaves fine.
→ I call them “manual page breaks” because they are not compile-format related.



PRINT PREVIEW :
COMPILED :
(Page break was ignored)
That is what I ended up doing…
But, I wanted to do it without splitting my original document, because :
1- I only wanted the splits (about 5 or 6) to be temporary (I actually resorted to splitting a duplicate of my original document for convenience) for a printout to which I wanted specific segments of a chapter isolated on their own page(s) to be able to physically reshuffle the order of those segments.
2- Using styles, I have my paragraphs numbered (you can see it in my “compiled” screenshot above → {1} {2} {3}… ). My compile format inserts a number <$n> reset at the start of each documents, so all my documents start with “paragraph 1”. → In this case I wanted my paragraphs to stay properly numbered without having to modify my compile format (which I ended up doing - had to remove that <$rst_n>).
3- When splitting a document, the snapshots stay with the top section of the document, and in this case, knowing that this was intended as a printout for further editing, I wanted to avoid having my document partitioned, with a section of it somewhere, and the corresponding past snapshots elsewhere.
This is something I am likely to do again in the future, so, it’d be good to know what is going on…
A setting somewhere ?
What could prevent the page breaks from compiling ?
(Since it seems to work fine when the paragraph has no style assigned to it - what I just found out -, I will make that my solution for the moment ; inserting any required page break as a “no style” paragraph of its own.)