Word's built-in styles can't be deleted. To be more precise, some built-in styles will generate an error message if you try to delete them, while others will not, but the result of the seemingly successful "deletion" is just that the style is returned to its default settings. However, these facts won't affect your custom styles in any way.

Keyboard shortcuts will save to the Normal template by default, but you can choose to save a shortcut to the template attached to the current document (in the Customize Keyboard dialog box).

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Stefan Blom
Microsoft Word MVP

Microsoft 365 apps for business
Windows 11 Professional