remove numbering in heading but keep the sub-heading numbering

Solution 1:

It looks like the numbering is calculated automatically, but we can work around this by formatting the numbering for Heading 1 so that it cannot be seen.

1. In the Character Styles sidebar, right-click on Default Style and choose New. Name it "Hidden".
2. Font Size: 2, Font color: white, check Hidden, OK.
3. Format -> Bullets and Numbering -> Customize. Level 1, Character style: "Hidden".
4. Go to Position tab. Level 1, Numbering followed by: Nothing.

More information about formatting the numbers:

• Change numbering color in LibreOffice Writer
• https://ask.libreoffice.org/en/question/60393/bold-numbering/