I'm really pleased with how my equivalent to Smart Objects turned out in Mojave Studio, my Mac image editor. In Photoshop you can transform an opaque sub-document with an affine and/or homographic transform, while in Mojave Studio you get what I call a "Smart Folder" shown inline, as if you're examining shadow DOM in web inspector. The thing you're viewing has its identity transform and the rest of the document gets the inverse transform applied, to see how it sits in context. https://mojavepaint.app/blog/smart-folders