How to organize a preview of the result of one psd file in another?

Question

PSD

I watched a video about how marmot makes its previews.

While watching, I noticed that after saving the preview, it goes to another PSD file and a new version of the preview is immediately substituted there.

So I wanted to know how to organize such a preview?
(if there is any template, I will gladly borrow it)

Answer 1

Smart Objects. Or rather, one smart object and its duplicates of the right size in different places.