Worked on the Godot editor within the godotengine/godot repository, focusing on resolving a user interface regression in the Theme Preview workflow. Addressed a bug where the '+' button was incorrectly positioned after dropping a new scene, ensuring the button’s placement aligned with expected behavior and that mouse events passed through as intended. Utilized C++ for editor and GUI development, implementing logic to dynamically resize preview tabs and maintain a stable layout. The solution restored smooth usability for Theme Preview tasks and included thorough validation to prevent future regressions, resulting in a targeted, maintainable fix with a clear change history for reviewers.