Outline numbering in lower level headings

[SDesmond]

I wanted to use Outline numbering starting in heading levels lower than
Heading 1. I want Heading 1, Heading 2, and Heading 3 styles to be without
numbering. Then I want the outline numbering to start with Heading 5. For
example:

Heading 1
Heading 2
Heading 3
Heading 4
1. Heading 5
1.1 Heading 6
1.1.1. Heading 7
2. Heading 5
2.1 Heading 6
2.1.1. Heading 7

I was able to do this in older version of Word. But every time I modify the
heading style, going into Format > Numbering > Outline Numbered and apply the
appropriate levels (i.e. level 2 to Heading 6) the Heading 6 reference
remains at level 6, even when I delete it and it resets to level 6 every
time, no matter how I configure it or clear the formatting.

It seems that there is an automatic reference or link that presets the
heading styles to outline levels. Does anyone know how to truly override
this? Like I said, I used to do this all the time in older versions of Word.