.DS_Store are invisible files that record settings for window appearance (and possibly other settings). They seem to be created when Show View Options ⌘J is used to customize a window. They're invisible because of the period at the front of the name. Used to be they were made visible when OnyX or another utility (or Terminal command) was used to make invisible files visible. Somewhere around 10.12 Sierra, Apple added a simple keyboard command ⌘⇧. (command-shift-period) to make invisible files visible. BUT at the same time, .DS_Store files were made super-invisible, so neither this command nor any utility I've found can make them visible. (Or they may no longer exist; I can't tell.) Does anybody know how to make .DS_Store files visible? Or if .DS_Store files no longer exist, is there something else that needs to be found and removed to reset a folder's appearance to default?