Create a Boost child theme called theme_boost_child with $THEME->parents= ['boost'] Ensure the lib.php of theme_boost_child contains an function theme_boost_child_get_pre_scss returning an empty string Ensure that theme_boost_child's config.php contains prescsscallback with value theme_boost_child_get_pre_scss Create a child theme of theme_boost_child called theme_boost_grandchild with $THEME->parents= ['boost_child','boost'] Ensure the lib.php of theme_boost_grandchild  contains an function theme_boost_grandchild_get_pre_scss returning an empty string Ensure that theme_boost_grandchild's config.php contains prescsscallback with value theme_boost_grandchild_get_pre_scss Set Moodle's design to theme_boost_grandchild Enable theme designer mode Load a Moodle page Ensure that the theme.css contains the following: /** Pre-SCSS from theme_boost_get_extra_scss **/ /** Pre-SCSS from theme_boost_child_get_extra_scss **/ /** Pre-SCSS from theme_boost_grandchild_get_extra_scss **/