This would be amazing. Also, not just for styles, but for other menus as well, such as property dropdowns or menus for swapping component instances. I think this would pair especially well with https://forum.figma.com/t/make-right-panels-larger-for-typography-color.
These are operations that we do every day hundreds of times. I would rather have this than some of the new features and capabilities. Working under deadlines is hard as it is. Don’t make it worse by making it difficult to find and select things in the menus and panels. That’s basic usability.