Dolphin actions can easily fill the notification history. They are usually created after resolving conflicts copying/moving files, or when transferring a large file. Mostly, they’re confirmations that everything worked.
I think that many of these events are not important enough to justify showing in history. It’s annoying having to dismiss these things all the time. Failed actions or long-running transfers would be great to keep in history, though.
you can configure all manner of notifications from other applications, or from the plasma shell itself, but dolphin is not listed among the applications and there is no file system notifications listed under plasma shell.
this would seem to be an omission, i agree.
at least firefox offers this where the button should be