> What isn't a content editor application? Well, anything that isn't a text/content editor (or a file system manager, which I had forgotten to mention), so bas

> What isn't a content editor application? Well, anything that isn't a text/content editor (or a file system manager, which I had forgotten to mention), so basically the vast majority of computer usage. Settings in applications, navigation state of applications, state of the OS/window manager itself (I'm not aware of a desktop environment where moving or closing a window or application supports an undo feature), etc. Web browsers and most file managers do support back and forward navigation, if you want to count that as "undo." The comment I was initially replying to talked about being afraid to press buttons in modern UIs because of the lack of undo. My claim is that, except for buttons that change formatting in text/content editors or buttons that make changes in some file system managers, undo functionality has really never existed to my knowledge.