Glyphs (the font authoring app for macOS) supports this workflow via their Smart Components feature. [1] The resulting outlines are "baked" when you build the f

Glyphs (the font authoring app for macOS) supports this workflow via their Smart Components feature. [1] The resulting outlines are "baked" when you build the final font, so this is a "compile time" feature, but the principle is the same. With variable fonts, you can get even interpolation between resulting forms "at run time". [1]: https://glyphsapp.com/tutorials/smart-components https://glyphsapp.com/tutorials/smart-components