Over a two-month period, mchagas worked on migrating key Thunderbird UI components to the Fluent localization framework within the thunderbird/thunderbird-l10n repository. They transitioned the Search Dialog and filter-related interfaces from legacy DTD and properties files to Fluent, enabling dynamic message handling and improved internationalization. Using FTL and focusing on UI/UX design, mchagas consolidated localization logic and introduced a new edit button to streamline filter management. The work laid a foundation for broader Fluent adoption, reduced future maintenance, and ensured localization consistency. Code reviews and integration checks validated the changes, reflecting a methodical approach to both technical migration and user experience.