Remark: as of the date of writing, 6.5.2 does not exist. Do you mean 6.3.5.2?
There are some subtleties with master and sub-documents.
Formatting occurs in the master document. The master imports the text from the sub-documents and uses its style definitions to lay out the paragraphs in the page(s). Only if the style does not exist in the master will the style definition be imported from the sub-doc. This means that master styles with same name override those in the sub-doc.
Unless you changed explicitly the font size in the sub-docs, all (master+subs) should have the same font size because you claim all are based on the same template. When you have a template, you don’t fancy yourself to add patches in some documents, which would ruin the interest of template.
Don’t worry about the 120% size instead of 28pt. %-sizes are just another way of specifying them. It guarantees to keep the same general relative ratios when you change a key style. All Heading n styles are relative to Heading style. When you changed the font style in the latter, all sizes in Heading n adjust accordingly.
Now to the main issue.
If you did not make vocabulary mistake, you tell us that you put your chapter heading (title) in the header, likely in the intention of repeating it on every page. This heading was styled Heading 1 as usual and I supposed you got the numbering too (1 because there is only one chapter per sub-document).
The header is an attribute of the page style.
As I explained above, the master uses its own styles when formatting the global document. Consequently, it does not reference the sub-document page style and does not import the header. You end up with no Heading 1 in your master and the TOC engine rightfully reports an empty table.
How to fix it?
It is very unusual to put the Heading 1 paragraph in the header. First reason, what will be its page number? It is duplicated on every page. Then it has multiple pages associated with it. The header is internally managed in a special way, it then probable that Writer will give it a single page number (first, last, other?) but this is not what you want to control.
Put your Heading 1 where it belongs, i.e. in the text area, not in header, not footer. This will fix the TOC issue.
If you want to repeat the chapter heading in the header, use field insertion.
In the master, modify the header to contain only Insert>Field>More Fields. Go to Document tab. In Type select Chapter and in Format Chapter name or Chapter number and name.
EDIT 2020-05-09
Your problem is quite simple. You have not understood the basic principle behind the styles concept.
Styles (whether paragraph or character) are used to mark up the structure of your text in semantic terms: some paragraphs are headings, others are “common” discourse, others source tagging (like Isaiah 63), others are comments, etc. The styles system is meant to explicit this structure. Primarily, it is not meant to confer typographical attributes to the text; this comes later when you try to show a reader how your text is structured.
Consequently, styles with names like “Head bold green” or “Head bold black” don’t make sense because you don’t indicate what they tag. They are just a reminder for which rendering you’d like the text to be formatted. On the contrary, a style like Psalm or Explanation has a real significance with regards to the text structure.
In the end, you’ll assign specific typographical attributes to those styles so that the content will stand out of the context and be identified as a specific component of your book.
A very important built-in family of styles is the Heading n set (n=1 to 10). They are provided as a very strong structuring function. Usually Heading 1 is used to flag chapter headings, Heading 2 for sub-chapters, etc.
This family is so important that it is collected by default to build the TOC. No paragraph (at least in the sample) has been styled Heading n; therefore the TOC will be empty.
To complicate matters, many paragraphs have their attributes set manually: the base style is Default Style and variants (font size, bold, colour) have been applied manually with toolbar buttons. The visual effect may be to give the appearance of a heading, but basically the paragraph remains a Default Style and is invisible to the TOC machinery.
As is, your master and sub-docs are unstructured and any attempt to make an elaborate synthesis out of it is doomed to fail. You must first restructure them. If you don’t know how to do it, I’d be glad to help you. Contact me privately on ajlittoz (at) users (dot) sourceforge (dot) net. This email address is given in an obfuscated form to protect me againt bots. Replace the descriptions within the parentheses by the single character and remove blanks. Once contact is made, you’ll have my real email address to start private discussion.
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