Main menu - View - Plain view - folders
Activating the main menu item "View → Plain view - folders" or the shortcut "Shift+Ctrl+B" activates this plain view for the active panel (this menu item is preceded by ), or deactivates it (it is preceded by ). If "Plain view - folders" is activated, only folders (and no files) are shown. The main folder and all sub folders are shown in one list, independent of their paths.
That a plain view is active, can be shown by highlighting the background color of the panel. This can be defined in the tab "Color/font" of the main menu item "Tools → Settings → View → File/folder list".
"Column profiles" with the assigned condition, that they are active, only if a "plain view" is active, can be defined under the main menu items "View → Column profiles → Settings" and "Tools → Settings → View → Column profiles".
It is also possible to change the status bar, if a plain view is active. For that, a status bar item has to be defined (under the main menu item "Tools → Settings → View → Status bar"), with the assigned condition: only active "For single selection plain view".
Attention: the display of the plain view could be slower than expected. It can be canceled with "ESC".