Window - Outliner.
By the way I strongly agree with the original post here. The Outliner is borderline useless. The funniest is copying a folder - it does exactly that. Copies the FOLDER, but NOT ITS CONTENT. It makes an empty folder with the same name. That’s what copying a folder means in Unreal. Ridiculous. Nesting is useless in much the same way. The fixed (alphabetical) order is just the cherry on top.
Please, do something about this. (Please… Is anyone there?..)