Legacy Component View is disabled by default. To enable Legacy Component View, edit your user preferences and set Enable Legacy Component View to Yes. See "Editing User Preferences".
Legacy Component View is a legacy user interface for editing application pages. Oracle recommends developers use Page Designer instead of Legacy Component View. Unlike Page Designer, Legacy Component View does not offer a visual representation of a page or support the dragging and dropping of page components. To preview the position of components on a page, you must run it. Also, some application components, such as interactive grids and Oracle JET based charts, cannot be edited or maintained using the Legacy Component View.
To assist developers with the transition to Page Designer, Page Designer includes a Component View tab. Similar in appearance to Legacy Component View, the Page Designer Component View tab presents user interface elements and application logic by component type. However, when you click a component and the Property Editor highlights the corresponding attribute in the right pane. See "Component View Tab".