Mahijith Menon worked on modernizing the user interface of the kestra-io/kestra repository by updating iconography to align with the project's design system. He replaced the legacy DotsSquare icon with the FolderOpenOutline icon across multiple Vue.js components, aiming to enhance visual consistency and reduce ambiguity in the UI. This change was implemented using JavaScript and Vue, focusing on front end development practices to ensure seamless integration. The update addressed a specific design issue tracked in the repository, resulting in a more polished and cohesive user experience. The work was limited in scope but demonstrated attention to detail in UI consistency.