We have to add custom classes and styles to SVG files in our products which requires hand coding. There is no design tool out there that won't completely destroy any hand-coded SVG styles or even attempt to work with them.
I make a rough draft of the icon in Figma or Affinity then export it and do the rest by hand and it can never be viewed in a visual editor again. Our design tools have failed us at providing good tooling for web and product work.