[Alcuin7]

Originally Posted by Tex2002ans

This type of formatting is very complex.

The only way you will be able to correct this is to get your hands dirty in the actual HTML.You'll have to go through your code, copy/paste them to their proper locations, and come up with all the proper HTML code to link them back and forth.

I was already digging into the HTML: that’s why I am here, looking for precisely what you are telling me. And a hearty and sincere “Thank you!” for your guidance!

For instance in the file index_split_006.html there is a primary (first-level) footnote (endnote) 31 with two explanatory secondary (second-level) footnotes (endnotes) numbered 32 and 33. The existing code in index_split_006.html reads (with line-breaks added to make it more legible),

<sup class="block_25">
<sup id="back_note_31" class="calibre10">
<a href="index_split_051.html#note_31" title="31" class="calibre2">
31
</a>
</sup>
</sup>
<sup id="id_Ref489614248" class="text_6">
<sup id="back_note_33" class="noteref1">
<a href="index_split_053.html#note_33" title="33" class="calibre2">
33
</a>
</sup>
</sup>

I moved endnote 32 before my initial post. It is in index_split_006.html as well, but has been cut-and-pasted to replace what had been a cross-link in Microsoft Word embedded into endnote 31 much further down in the html. (Again, line-breaks added)

<sup id="id_Ref489614211" class="text_6">
<sup id="back_note_32" class="noteref1">
<a href="index_split_052.html#note_32" title="32" class="calibre2">
32
</a>
</sup>
</sup>

If I understand what you have written, what I have observed in the code, and the behavior of the EPUB document, when asked to return to the calling point for note 32, the code searches (sequentially?) for “index_split_052.html”, and not finding it in its expected place following index_split_051.html, returns the reader either to that point (the marker for note 31) or to index_split_053.html (the marker for note 33).

1. Are you saying that I need to use another format of endnote markers, say {a, b, c, …}, to identify my second-order notes, and maintain them separately from the first layer of endnotes? I don’t suppose I can begin renumbered them from {a} every time I begin a new endnote with endnotes attached to it? I have 52 sub-notes, and while some of them are tertiary notes (third level), I should run into double-letter note markers (i.e., {aa, ab, ac, …}). This isn’t a problem, but if the tertiary (third level) are numerous – I haven’t counted how many there are – I could be running into four or five asterisks and daggers unless the symbols have their own specified order in Calibre.
2. I assume I must also renumber “index_split_nnn.html” sequentially throughout the document so that they are in their correct order. I think that is clear from your post. There are 454 htmls numbered index_split_000.html to index_split_453.html. I can either export them one-by-one or copy-and-paste them, but that is a real pain for so many pieces of the document. Is there some way to access them all? because if there is, then this becomes a fairly standard search-and-replace hack with external code.
3. I am delighted that you have answered this query, Tex2002ans. Since I know you are also familiar with MOBI, can I straightforwardly convert the EPUB (once I have it) into MOBI without further manipulation? And how do I prevent MOBI from justifying the text, but keep it aligned left?

Many, many thanks! I will begun perusing the HTML in your example EPUB from Jean-Baptiste Say for exemples. You built this with Sigil rather than Calibre? Making the footnote-in-footnote changes manually? Do I need to switch to Sigil? (I don’t want to do that if I can help it.)

Originally Posted by Tex2002ans

...what happens in the Word DOCX if someone clicked the cross-link? How are people supposed to read these footnotes in footnotes if they're size 1 and white text?

You misunderstand. There is no way to embed footnotes into footnotes in Microsoft Word. It is accomplished by entering separate footnotes, formatting and cross-linking them so that they appear to be footnotes to footnotes, then hiding the real footnote markers.

In my Word Document, the embedded footnotes follow immediately after the main footnote, [31][32][33] in this example. In footnote 31, text “32” and “33” are put in their proper positions in footnote 31, superscripted, then cross-linked to the real footnotes 32 and 33. That highlights them and makes them accessible by clicking on them. Then the text for the real footnote markers in the main body of the book (not the footnotes themselves) is reduced to font size 1 and colored white: the real markers are no longer visible. It appears to anyone reading the text that there is nothing there but a clickable marker for footnote 31 (followed perhaps by an unusually wide space), while the secondary “footnotes” appear to be in their proper (cross-linked) places in footnote 31. It looks fine in Word and prints correctly, except for the space behind the footnote marker for [31], which is small enough to escape notice.

But this method does not transpose to EPUB or MOBI after conversion.