OK, I think I've figured out.
https://github.com/koreader/crengine.../data/epub.css
From line 11 to 24
Code:
/* EPUB container of each individual HTML file */
DocFragment {
page-break-before: always;
}
/* Non-linear fragments (hideable) */
DocFragment[NonLinear] {
-cr-hint: non-linear;
}
section[type=footnotes] {
-cr-hint: non-linear;
}
aside[type=footnote] {
-cr-hint: non-linear-combining;
}
As long as you have one of the following HTML tags in your epub file:
- <aside epub:type="footnote">XXX</aside>
- <section epub:type="footnotes">XXX</section>
You will have "Hide Non-linear Fragments" option.
Of course, your epub must be Epub3 which supports those tags.