1. A method comprising: at an electronic device with one or more processors and memory: generating for presentation on a display a user interface including a plurality of groups of icons, wherein the user interface has first and second modes, and a plurality of the icons have been grouped based at least in part on metadata of applications associated with the icons; receiving input selecting a respective icon; in response to receiving the input selecting a respective icon, invoking an instance of an application associated with the respective icon; receiving input requesting adding an additional application; in response to receiving the input requesting adding the additional application: in accordance with a determination that metadata of the additional application indicates an icon associated with the additional application should be displayed in a first group of icons, adding the icon associated with the additional application to the first group of icons; and in accordance with a determination that the metadata of the additional application indicates the icon associated with the additional application should be displayed in a second group of icons, adding the icon associated with the additional application to the second group of icons; receiving scrolling input scrolling the plurality of groups of icons; and in response to receiving the scrolling input scrolling the plurality of groups of icons: in accordance with a determination that the user interface is in the first mode, scrolling the plurality of groups of icons in proportion to a magnitude of the scrolling input; and in accordance with a determination that the user interface is in the second mode and that the scrolling input meets one or more group-scrolling criteria, scrolling the plurality of groups of icons from a first group to a second group.