This command does not work on child windows. Therefore it doesn't work on buttons that are part of a panel. You can make such buttons invisible with HideWin.
This command does not work on all windows but it does work on HotkeyNet's panels.
This command affects the window that was previously targeted with TargetWin, SendWin, etc.
You can use SetPanelStyle to make a panel's background invisible so only the buttons can be seen and clicked.