Odoo-Build/snippets/stock.view_picking_form.modify_invisible_button_validate.xml

<?xml version="1.0"?>
<data inherit_id="stock.view_picking_form" priority="50">
    <xpath expr="//button[@name='button_validate']" position="attributes">
        <attribute name="attrs">{'invisible': ['|', '|', ('state', 'in', ('waiting','confirmed')), ('show_validate', '=', False), ('started', '=', False)]}</attribute>
    </xpath>
</data>