Use the Modify Style dialog box for Heading 1 to access the list numbering (as detailed in Shauna's article).

For level 2, delete the content of the "Number format" box and recreate it by adding the current level number from the "Number style" box and add level 1 from the "Previous level number" box. Type in the period.

When you are done, click OK repeatedly to close all dialog boxes.

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Stefan Blom
Microsoft Word MVP

Microsoft 365 apps for business
Windows 11 Professional