How to decrease space between site title and navigation?

Q2: Is there a way to do this in the customizer, and not by adding additional CSS code?

You can’t be helped without sharing site link. Anyway, try setting the navigation to float left in the customizer.

That doesn’t help, the navigation needs to be centered not left.

My question is how to make it closer to the site title.

Can you link us to the page in question?

Thanks!