how do I add a grid section?

Site URL: https://rectangle-rhombus-8f5s.squarespace.com/cascade

I somehow added this magic section with a dragable grid. I have no idea how I did it and how to do it again.  help?

It looks like you used Fluid Engine. 

See this. https://support.squarespace.com/hc/en-us/articles/6421525446541-Fluid-Engine-Squarespace-s-new-content-editing-experience

That's it! but it happened only ONCE on the site, but now every time I add a new page/ blank section it does not give me this option?  

I have same problem 😆

You try posting to Circle Forum.

On 6/14/2022 at 2:34 PM, sarahetts said:

That's it! but it happened only ONCE on the site, but now every time I add a new page/ blank section it does not give me this option?  

@sarahetts On June 15, Squarespace announced and gave access to its new drag-and-drop editor, Fluid Engine, that @tuanphan cited above, to Circle Members. When you duplicate a section or page created in the 7.1 Classic Editor, you can use CE or change to page or section to FE. When you convert to FE, be mindful that you cannot convert back to CE. When you create a new section or page, FE is the default editor.