You can set recurring maintenance windows as an account preference or at the level of an individual monitor. One-time maintenance windows, on the other hand, can only be set at the account level. When a recurring maintenance window is set as an account-level preference, it can either be applied to all the existing monitors in the account or to both existing monitors and monitors yet to be created.
Account-level maintenance windows can only be managed through the Synthetic Classic Portal. See Maintenance Windows for details.
Only users with the Account Primary, Account Admin, or Test Admin profile can manage maintenance windows.