In the Styles and Formatting pane, the styles on top are the most recently used ones, yes.

The Modify command can be used to change the style definition, which applies to all paragraphs using that style; that is correct. If you are changing the numbering, always start with the level 1 style (for example, Heading 1 for outline-numbered headings).

Note that you can control which styles show up in the task pane. In the "Show" box, click the "Custom" option and make your changes in the Format Settings dialog box.

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Stefan Blom
Microsoft Word MVP

Microsoft 365 apps for business
Windows 11 Professional