A family of Microsoft word processing software products for creating web, email, and print documents.
If you are using custom paragraph styles for these headings, just set up a multilevel list using these custom styles. The principles discussed at https://www.brandwares.com/bestpractices/2016/06/outline-numbering-in-word-for-os-x/ apply.
To map your styles to levels 7, 8 and 9, use a field code such as:
{ TOC \t "Custom style 1,7,Custom style 2,8, Custom style 3,9" }.
You can edit the field code if you first display field codes (Option+F9 in Word for Mac).