All the reports, both created for export and scheduled, are saved in the Reports section within Ads Manager. From there, you can download, duplicate, edit or delete the reports that are no longer in use from the list. 

All users with access to the Ad Account can view all reports created within it. The report owner is displayed in the 'Created by' column. Admins and Contributors can manage (edit and delete) reports by any user, while Viewers can edit any report but cannot delete those created by others.