[jdright]

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

[alpaca128]

Probably the three-column view where you see the parent folder, current directory and selected folder's contents side by side.

[andrekandre]

it goes more than 3 columns, its more like drill-down view and very handy... its something i miss from macos too

https://www.lifewire.com/use-finder-views-on-mac-2260734