For example i have

'property_account_position': fields.property(
            'account.fiscal.position',
            type='many2one',
            relation='account.fiscal.position',
            string="Fiscal Position",
            view_load=True,
            help="The fiscal position will determine taxes and accounts used for the partner.",
        )

1 way :

inherit model and redefine field

'property_account_position': fields.property(
            'account.fiscal.position',
            type='many2one',
            relation='account.fiscal.position',
            string="Fiscal Position",
            view_load=True,
            help="The fiscal position will determine taxes and accounts used for the partner.",

required=true,

        )

but i think it's not good redefine field just to set it required or set new caption

2 way:

set required in xml

<field name="property_account_position" position="replace">

<field name="property_account_position" required="true"/>

</field>

but in this way i need to set it all xml views

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May be here is a good way just set some field option ?

something like field_name['option_name'] = new_value