To compile composite table of content

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Build ID: 40(Build:1)
CPU threads: 2; OS: Linux 5.15; UI render: default; VCL: gtk3
Locale: en-US (en_US.utf8); UI: en-US

One .odt document with three levels chapter, sub-chapter numbering (numbering scheme 1., 1.1, 1.1.1). Heading 1, Heading 2, Heading 3 paragraph styles in use.
Adding table of content built from chapters + sub-chapters headings (2-levels) to document was trouble free.

Document last page(s) includes bibliography generated by external reference manager.
Bibliography headline use separate paragraph style: Bibliography Heading, as well as list style ‘No list’
as well as no numbering is used that headline.

At later point of time appendices are going to extend table of content. All appendices however are - as of time being - stored to separate file. The preference is to let it be this fashion as this way main document handling/editing is much easier than with everything merged to one single document. Appendix headings use alphabetic numbering yet one heading style (paragraph style) of same name is used Heading 2.
Eventually this is additional reason to let appendices be in separate document.

  • What is the best way to add appendices to table of content?

Also at later point of time few object indices might need to be added to table of content. These however still don’t exist as of this minute.

It is usually recommended to ask one question per topic. Here your questions, though loosely related, are quite different IMHO.

How to add bibliography heading to TOC ?

Since you have a separate paragraph style for you bibliography, namely Bibliography Heading, customise this paragraph style:

  • go to Outline & List tab
  • attach the paragraph style to the ad-hoc Outline level using the drop-down menu

Using a different numbering scheme for appendices

You write you want to “extend” your existing TOC with alpha-numbered appendices. There is no other way than to make the appendices visible from the document main part.

So, either you write directly your appendices in the document (or insert the text through Insert>Text from File) or, if you want to keep your appendices as separate files, turn your main document into a master and reference the appendices from there.

Either way this needs dedicated paragraph styles to number the appendices because Tools>Chapter Numbering supports only a single scheme and only one paragraph style can be attached to any level.

The trick is to duplicate the Heading n family into an Appendix n family. In order to guarantee formatting consistency between chapter and appendix headings, the simplest method is to right-click on each Heading n and New. This creates an exact copy of Heading n which inherits everything from it and is updated when you modify Heading n.

Your clones are “ordinary” paragraph styles at Text Body level without numbering. You must create a list style for your purpose. Call it Appendix. Choose the numbering scheme and give it the same “geometry” parameters as Heading n (indent, alignment and tab stop). Associate your Appendix n to Appendix in Outline & List tab.

This new “chapter” hierarchy is not managed automatically like Heading n. This means you must set the level yourself for appendix, sub-appendix, sub-sub-appendix, …

When you create an appendix, style its heading as Appendix 1. By default it is at level-1 like in every list. To enter a sub-appendix heading, style it appendix 2 and at the very beginning of the heading press once Tab. Similarly, for an appendix sub-heading at level-n, style it Appendix n and press Tab n-1 times.

Thanks for hints.
Fortunately appendices use 1-level numbering (no sub-chapters) at their headings. I hope me can keep it this form till editorial deadline.

Me conducted following steps in the second document of appendices

  • created duplicate of paragraph style Heading 1
  • copied geometry from paragraph style Heading 2 to duplicate created newly or let latter one unchanged depending on which of these two will provide consistent end presentation
  • reassigned headline of each appendix to Heading 1 duplicate
  • created new list style, with numbering format ABC
  • assigned duplicate of Heading 1 to new list style
  • promoted duplicate of Heading 1 to single level chapter numbering

Appendices, or just their headlines, are ready now to transport to main document.

Any gaps or mistakes in understanding above?

I am going to transport to main document
Headline of every appendix (no sub-appendix exists)
New list style
Page style used by appendices, as page numbering differs from main text