NFT: Coding/Squarespace question - Flatiron theme

Random question here.

I'm working on building a website utilizing the Flatiron theme in Squarespace. I'm trying to build something similar to THIS DESIGN HERE, where when you click on the thumbnail from the gallery, you can prompt a Vimeo Lightbox to pop up. So far I've read that this isn't possible in a traditional sense with the Flatiron theme, but there is custom Javascript you can use to override this and prompt the light box (as opposed to it just loading the video on a new page).

Does anyone have anyone know where I can find a snippet like that or have experience implementing it yourself?

Thank you very much in advance.