Hi,

 In the Time Off types of Odoo Time Off module, you can configure the criteria for approval of time off requests. You can choose the "No Validation" option to bypass time off approvals. Alternatively, you can select "By Time Off Officer" or "By Employee's Approver" as the approval method. The request requires two approvals to be confirmed if both "By Employee's Approver" and "Time Off Officer" are selected.

If you want to add a third approval or more to the approval process of the Time Off app, you can use a module for multi-level approvals in Time Off, which can configure the approver in each Time Off type.

Hope it helps