not sure what he means by columns either. but split view on dolphin exists for many years already.

A full-featured columns view, like that of macOS (but also implemented by various file browsers over the years), has an arbitrary number of resizable columns. Perhaps optionally with a preview pane at the end where the last column would otherwise be.

You can get the gist of it from this Super User discussion: https://superuser.com/questions/1141631/make-windows-10-file...