Lower horizon of Nishita Sky when sun turned on?

I’m able to lower the horizon when I turned of the sun disc by rotating the connected vector. But when turning on the sun disc, there is no longer a vector socket. So how can I do that?

The altitude slider controls the horizon as far as I can tell. You can’t actually go negative though, is that what you’re after?

The altitude only change the color of the sky. I think I have to create a sun manually. Thanks!