Using previously un-used heading levels would be more suitable for situations where you want to maintain two separate numbered lists that both make use of the "magic" properties of the built-in headings; for example, this would be the case when you set up appendix numbering as discussed in the article at
In the Adobe InDesign document I’m working on here we actually have two master pages, an ‘A’ master and a ‘B’ master so I’m going to select both the left and right hand page frames with the special character in on my ‘A’ master and go to Edit>Copy. I’m then going to double click on my ‘B’ master page and go to Edit>Paste in place. this will then copy the special character and position it in exactly the same place as it appears on my ‘A’ master. numbering in publisher