Hi,

Create a new field sequence then add that to the pos.payment.method then update the pos.session _loader_params_pos_payment_method function to order by the sequence field

class PosPaymentMethod(models.Model):
    _inherit = 'pos.payment.method'

    sequence = fields.Integer('Sequence')


class PosSession(models.Model):
    _inherit = 'pos.session'

    def _loader_params_pos_payment_method(self):
        res = super()._loader_params_pos_payment_method()
        res["search_params"]["order"] = 'sequence asc, id'
        return res

Regards