Hello Julian.
Under Windows, please, replace the code in the SplashScreen::show(…) function
from this:
addToDesktop (useDropShadow ? (ComponentPeer::windowAppearsOnTaskbar | ComponentPeer::windowHasDropShadow)
: ComponentPeer::windowAppearsOnTaskbar);
to this one:
this will prevent a splash screen window from appearing on the taskbar. I think it is the more natural behaviour for splash screens.