CSS preprocessors have had nesting support for a long time, and it is now natively supported in CSS as well. Furthermore, many browsers already provide support for CSS nesting already: https://caniuse.com/css-nesting
CSS nesting is a valuable tool, which has many advantages, including enhanced code readability and organization, which ultimately contribute to the improved maintainability and efficiency of the CSS stylesheets. Therefore, adding this functionality to OutSystems would be beneficial.