https://github.com/bitcoin/bitcoin/blob/5180a86c96bc05d2a731f70f36aae28ab5a3fad4/src/qt/sendcoinsdialog.cpp#L339

I think this is %1, not %2
msgParams.second = CClientUIInterface::MSG_ERROR;
        break;
    case WalletModel::AbsurdFee:
        msgParams.first = tr("A fee higher than %1 is considered an absurdly high fee.").arg(BitcoinUnits::formatWithUnit(model->getOptionsModel()->getDisplayUnit(), maxTxFee));
        break;
    case WalletModel::PaymentRequestExpired:
        msgParams.first = tr("Payment request expired.");
        msgParams.second = CClientUIInterface::MSG_ERROR;
        break;
    
    case WalletModel::OK:
    default:
        return;
    }
    Q_EMIT message(tr("Send Coins"), msgParams.first, msgParams.second);
}
void SendCoinsDialog::minimizeFeeSection(bool fMinimize)
{
    ui->labelFeeMinimized->setVisible(fMinimize);
    ui->buttonChooseFee  ->setVisible(fMinimize);
    ui->buttonMinimizeFee->setVisible(!fMinimize);
    ui->frameFeeSelection->setVisible(!fMinimize);
    ui->horizontalLayoutSmartFee->setContentsMargins(0, (fMinimize ? 0 : 6), 0, 0);
    fFeeMinimized = fMinimize;
}
void SendCoinsDialog::on_buttonChooseFee_clicked()
{
    minimizeFeeSection(false);
}
void SendCoinsDialog::on_buttonMinimizeFee_clicked()