All "containers" should be shown in the same place, with the same functions across the desktop/mobile scene. This is an example of how the Files app can be implemented across form factors. I propose that the app's elements be divided into classes, i.e. utility pane, like the bookmarks bar; content, always the immediately visible/accessible one; status, as in currently playing track or current directory; etc. That way you always have your content up front and useable, while your accessory panels are always in the right place just waiting for your input.