Noticed this while reviewing #13529, but it's also in master @ 5ba77df. On macOS 10.13.6:

<img width="209" alt="schermafbeelding 2018-08-01 om 16 22 09" src="https://user-images.githubusercontent.com/10217/43527498-0f571db4-95a7-11e8-8d90-7863947a7689.png">


<img width="178" alt="schermafbeelding 2018-08-01 om 16 12 51" src="https://user-images.githubusercontent.com/10217/43526994-c9a515ec-95a5-11e8-96b8-9e2513e9aac5.png">

* `Show` in the action menu doesn't work if the app was hidden by `Command + H`, it does work when hidden through this menu
* send and receive don't unhide the window when opened for the action menu. It does navigate to the right tab. The other actions do work (sign, verify & debug window)

Clicking "Toon" (= macOS native show) does work, suggesting the GUI uses some non-native method of hiding.
openAction->setStatusTip(tr("Open a bitcoin: URI or payment request"));
    showHelpMessageAction = new QAction(platformStyle->TextColorIcon(":/icons/info"), tr("&Command-line options"), this);
    showHelpMessageAction->setMenuRole(QAction::NoRole);
    showHelpMessageAction->setStatusTip(tr("Show the %1 help message to get a list with possible Bitcoin command-line options").arg(tr(PACKAGE_NAME)));
    connect(quitAction, &QAction::triggered, qApp, QApplication::quit);
    connect(aboutAction, &QAction::triggered, this, &BitcoinGUI::aboutClicked);
    connect(aboutQtAction, &QAction::triggered, qApp, QApplication::aboutQt);
    connect(optionsAction, &QAction::triggered, this, &BitcoinGUI::optionsClicked);
    connect(toggleHideAction, &QAction::triggered, this, &BitcoinGUI::toggleHidden);
    connect(showHelpMessageAction, &QAction::triggered, this, &BitcoinGUI::showHelpMessageClicked);
    connect(openRPCConsoleAction, &QAction::triggered, this, &BitcoinGUI::showDebugWindow);
    
    connect(quitAction, &QAction::triggered, rpcConsole, &QWidget::hide);
#ifdef ENABLE_WALLET
    if(walletFrame)
    {
        connect(encryptWalletAction, &QAction::triggered, walletFrame, &WalletFrame::encryptWallet);
        connect(backupWalletAction, &QAction::triggered, walletFrame, &WalletFrame::backupWallet);
        connect(changePassphraseAction, &QAction::triggered, walletFrame, &WalletFrame::changePassphrase);
        connect(signMessageAction, &QAction::triggered, [this]{ gotoSignMessageTab(); });
        connect(verifyMessageAction, &QAction::triggered, [this]{ gotoVerifyMessageTab(); });
        connect(usedSendingAddressesAction, &QAction::triggered, walletFrame, &WalletFrame::usedSendingAddresses);
        connect(usedReceivingAddressesAction, &QAction::triggered, walletFrame, &WalletFrame::usedReceivingAddresses);
        connect(openAction, &QAction::triggered, this, &BitcoinGUI::openClicked);
    }
#endif 
    connect(new QShortcut(QKeySequence(Qt::CTRL + Qt::SHIFT + Qt::Key_C), this), &QShortcut::activated, this, &BitcoinGUI::showDebugWindowActivateConsole);
    connect(new QShortcut(QKeySequence(Qt::CTRL + Qt::SHIFT + Qt::Key_D), this), &QShortcut::activated, this, &BitcoinGUI::showDebugWindow);
}
void BitcoinGUI::createMenuBar()