Course overview is the one of the best feature in moodle. this feature can be extended by suporting this bar for sections/topics. at this time one such theme ( [moove|https://moodle.org/plugins/theme_moove] ) is supporting this feature . https://moodle.org/plugins/theme_moove .
but unless moodle core supports it it can not be implemented in moodle mobile. its my request to consider this festure in moodle roadmap. undoutedly this will enhance user experience.