Using master (98958c81f5065a5de13699d46995d278ecb6709e) with Qt `5.12.3` (also tested with depends) with multiple wallets available. None are shown in the `Open Wallet ->` menu in the gui. The wallets can be loaded from the console, bitcoin-cli etc.
QAction* m_close_wallet_action{nullptr};
    QAction* m_wallet_selector_label_action = nullptr;
    QAction* m_wallet_selector_action = nullptr;
    QLabel *m_wallet_selector_label = nullptr;
    QComboBox* m_wallet_selector = nullptr;
    QSystemTrayIcon* trayIcon = nullptr;
    const std::unique_ptr<QMenu> trayIconMenu;
    Notificator* notificator = nullptr;
    RPCConsole* rpcConsole = nullptr;
    HelpMessageDialog* helpMessageDialog = nullptr;
    ModalOverlay* modalOverlay = nullptr;
#ifdef Q_OS_MAC
    CAppNapInhibitor* m_app_nap_inhibitor = nullptr;
#endif
    
    int prevBlocks = 0;
    int spinnerFrame = 0;
    const PlatformStyle *platformStyle;
    const NetworkStyle* const m_network_style;
    
    void createActions();
    
    void createMenuBar();
    
    void createToolBars();
    
    void createTrayIcon();
    
    void createTrayIconMenu();