Desktop mini-player window

The mini player is not a second application. It is one more window in the same application composition, whose existence is a boolean and whose contents read the same state holder the main window reads:

// adapted
application {
    Window(onCloseRequest = { isVisible = false }, visible = isVisible, …) { App() }
    if (MiniPlayerManager.isOpen) {
        MiniPlayerWindow(
            stateHolder = playerStateHolder,
            onCloseRequest = { MiniPlayerManager.isOpen = false },
        )
    }
}