Nothing out-of-the-box is going to do what you want.

Here is the ribbon version of Shauna Kelly's article which implements John McGhie's observations.
How to create numbered headings or outline numbering in Ribbon Versions of Word by Shauna Kelly
Follow her instructions completely. Do not skip steps.

Those two articles are the best information I know of for implementing numbering in Word.

You will find links to both of them in my chapter on Numbering in Microsoft Word.
That chapter also goes into the SEQ field.