Volto: How can I have overideable themes/ css in an addon?

I would like to include some custom LESS/ CSS in an addon. Currently the less is stored in a .overrides file in the theme (overriding some css for the toolbar). The add-on docs suggest that I can use razzle to alias the root theme from the add-on, but this would replace the theme entirely. (8. Add-ons - advanced topics – Volto Add-ons Development — Plone Training 2022 documentation and volto/index.md at master · plone/volto · GitHub). Is there a better approach to including custom CSS/ LESS that would still allow for using the Volto theming mechanics in the root project?

See this example: volto-columns-block/columns.less at master · eea/volto-columns-block · GitHub

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