If you want to change the options or parameters for a task you set before, please click Backup and recovery tab, and distinguish the task you want to modify through name, created time or other information, and then click 'Edit backup'. In the window, all parameters can be modified. Please notice that all the changes only take effect for the following task and will be available after you save the changes.
You can still directly start edit backup from the Backup and recovery page by clicking Advanced --> Edit backup.