Hi,

You can try custom module :  Sales Order Double Approval

Hope it helps

Hi,

If you are using odoo enterprise, you can use the approval in studio.

* Open the sale order form
* Enable studio
* Click the button to which you need the approval

And you can configure the approval condition and which user group needs to do the approving.

For More:  Odoo Studio: approvals and workflows

If you are using community edition, there are third party apps providing this feature, you can check out for the same

Thanks