On one line, type the heading text that will be visible, e.g.Introduction), use both styles as follows: Set up the other numbering levels in the usual way.In the multilevel numbering dialog, ensure that the level 1 numbering is linked to the Heading 1 style (you will need to click the MORE button to see the linked style option).Then set up your multilevel numbering definition: Instead of Heading 1, you could use another custom style that you create. Most importantly, in the Style definition dialog, click the Format button then choose Font, then check the Hidden check box. From the style gallery on the Home ribbon, right-click and modify the Heading 1 style.
You still need to keep the conventional structure of 1 (level 1, Heading1 style) and 1.1 (level 2, Heading2 style) so that 1.1 progresses to 2.1, 3.1, 4.1 etc. Yes, it’s certainly do-able and it’s a question that’s come up before in various forms.