Translations:New Template System in LS3.x/28/en

The Simple option page comes from the Template itself. It’s made via a twig file and some javascript inside the theme's /options directory: https://github.com/LimeSurvey/LimeSurvey/tree/develop/templates/default/options (Broken link)

This page can be completely different from a theme to another, and theme providers are strongly encouraged to create their own look & feel.