Tom I would say in Webflow hitting G on your keyboard and hitting the little brush icon top right will clean up any unused styles.
If you created custom classes that you are only using in code embeds, you'll wipe those away if you use this tool - so just put a div with those custom classes somewhere on the style guide page and you'll be fine. All other global utility classes used to do layout and other things should already be on the style guide page so using this tool won't hurt anything. Not a bad idea to do a backup before doing it though (cmd + s to do a backup snapshot in Webflow).
In Webflow, using the Finsweet tool, you can rename classes in bulk using the Folders feature. We have a quick doc on that here:
https://www.relume.io/resources/docs/working-with-finsweet-tools#folders
Hope that helps, Viktor covered the Figma side, so if neither of these is what you meant or if we didn't answer your question - feel free to expand on it more with some examples as well.
