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.
{
    std::string chain = gArgs.GetChainName();
    if (chain == CBaseChainParams::MAIN)
        return GetAutostartDir() / "bitcoin.desktop";
    return GetAutostartDir() / strprintf("bitcoin-%s.lnk", chain);
}
bool GetStartOnSystemStartup()
{
    fsbridge::ifstream optionFile(GetAutostartFilePath());
    if (!optionFile.good())
        return false;
    
    std::string line;
    while (!optionFile.eof())
    {
        getline(optionFile, line);
        if (line.find("Hidden") != std::string::npos &&
            line.find("true") != std::string::npos)
            return false;
    }
    optionFile.close();
    return true;
}
bool SetStartOnSystemStartup(bool fAutoStart)