You can use SEQ fields for this kind of numbering. Where does the "2" come from in "2.3"? If it is supposed to be the number of a heading style, you can retrieve it using a STYLEREF field. For example:

{ STYLEREF 1 \n }.{ SEQ MyEq \s 1 }

The "1" refers to the built-in Heading 1 style. "\s 1" instructs Word to restart the numbering following each Heading 1 paragraph in the document.

Here is how to create the fields: Press Ctrl+F9 to insert each pair of field delimiters, { }. Type in the code as shown. Press F9 to update.

To show/hide all field codes in a document, press Alt+F9.

You can use copy and paste to duplicate the fields, but you will have to force an update of the SEQ fields by switching to Print Preview and then back to your previous view (you can use Ctrl+F2 followed by ESC).

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Stefan Blom
Microsoft Word MVP

Microsoft 365 apps for business
Windows 11 Professional