The Lock/Unlock functionality still exists in Odoo 17 but has been relocated to improve the user interface organization. 

Location in Odoo 14: The Lock and Unlock buttons were displayed as separate, visible buttons directly on the inventory transfer form view.

Location in Odoo 17: These functions have been moved to the Action menu (⚙️ icon) in the inventory transfer form. To access them: (After Validation)

1. Open your inventory transfer
2. Click on the "Action" button in the top menu
3. Select either "Lock" or "Unlock" from the dropdown menu options
   
                      

Regards

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NIZAMUDHEEN MJ