You can easily set up this multi level sequential approval flow using Odoo Studio on the Purchase Order form. here are the steps you can follow;

1. Open the Purchase module and enter the Form view (RFQ/Purchase Order).

2. Open Odoo Studio ,Navigate to the "Confirm Order" button and click on it to open its properties panel.

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5. Click on approval Step, You can set the condition for triggering the approvals. if you want to apply to all RFQ/PO, you can set this condition.
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10. After confirmation, you can assign the relevant approvers and approver group. Set up the first approval by setting approval order as 1 , and for the second approval, for the manager's confirmation, set the approval order to 2.

Kind Regards,

Muz