Yes, you can make different styles with different attributes for use in different areas of the doc. These don't need to only use the built-in heading styles although there are benefits to using those rather than creating custom styles.

You can then specify the TOC in different ways to get to what you want. For instance, a TOC field code can include paragraphs based on outline levels and/or specific style names.
{TOC \o "1-4"} will include Heading 1 as TOC 1, Heading 2 as TOC 2 etc but this would also include any other styles that have their outline level set to 1, 2, 3, or 4. The TOC number will align with the outline level assigned to the trigger style.

{TOC \t "Heading 1,1,Head1,1,Heading 2,2,Head2,2"} will include 4 styles mapped to TOC 1 and 2 irrespective of the 'outline' level assigned to those styles.

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Andrew Lockton
Chrysalis Design, Melbourne Australia