How to reduce block spacing???

My blog posts often have quotes at the top that are framed by horizontal lines (separators). Before Gutenberg, I could use Shift+Enter to place the horizontal lines immediately before and after the quote, which creates a nice effect. (Example: https://www.katiescolitisjournal.com/awake-the-real-band/) How can I create that same effect with Gutenberg? Since I now have to add separators as their own blocks, they are automatically spaced far away from the quote text, creating way too much space at the beginning of the blog post. I want to reduce the spacing between blocks, or fake it by reducing the paragraph margins on the quote. (I don’t have an example of the “bad” spacing yet–it’s on an upcoming post and I’m hoping to fix this problem BEFORE posting.)

I’m not a coder, but is there a way to do this in the Additional CSS class box, perhaps? Or some other way?

(I hate Gutenberg so far! I just want to blog; I don’t want to spend my time learning a whole new system. ?? )

The page I need help with: [log in to see the link]