Pasting content into blog posts adds dozens of line breaks - how to prevent this?

I've had this problem for a couple of years now and it adds so much time to my site processes I'm wondering if anyone else has the issue and if there's a way to prevent it.

I write long blog articles (5000-10,000 words) so I write these in a Google doc then when they're complete I copy and paste into my Squarespace blog.

When I paste them in, each single line break from the Google doc = 12+ line breaks in Squarespace.

So every new title, heading or paragraph has at least 12 line breaks below it once I've pasted it into Squarespace, despite there only being 1 regular line break in my Google doc.

This then means I spend 30-60 minutes per upload having to manually remove all the additional line breaks in a 5000+ word blog post.

Does anyone know why this happens or how I can avoid it?

It happens when I paste and paste as values too - although I'm often including URLs in my article so pasting as values or pasting into notepad first is not a solution.

Thanks!

Can you share link to a post where you have problem? We can take a look