Take a document that contains all your custom styles and save it as a template.

After that you might want to get rid of all the content that isn't needed. The styles will remain.

Then you might apply the styles to examples, such as the word "heading" with the heading style applied to it.

When you need to recover the styles in a different document, go to "Manage Styles" in the Styles menu and choose "Import/Export." Both windows will show the current document. Close that in one of the windows and open your template instead. Then you can copy the styles to the other window, choosing to overwrite what's in the open document (not in the template).

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