Using this CSS

In this project there is a default.css and an autonum-headings.css.

When you generate an output where you don't want numbering, use default.css or your own css.

When you want numbering such as in a printed document, go to Reports > Topic List and select all topics (check box top left). Then right click and select Properties. Under Style Sheets add the autonum-headings.css.

When done, reverse the process.

If you always want numbering, you can copy the contents of autonum-headings.css into your own css.