In Fullscreenmode using custom skins and 'vlc.onTop()' enabled shows mainwindow as tooltip
Use a custom skin with a fullscreen controller (for example default.vlt). Play any video and enable 'always on top'. Switch to fullscreen and hover over any element of the fullscreen controller that has a tooltip (for example 'show playlist').
Besides the tooltip the main window appears as well.
VLC Version 2.1.5 Ricewind