Flat View
Flat View is a mode you can turn on in a Lister that enables you to view all the contents of a folder's sub-folders at once. In effect it collapses, or flattens, the display of a nested hierarchy of folders and files into a single folder.
If you want to be able to control which folders are expanded, expandable folders may be a better choice. Flat View is similar to expandable folders, except it expands everything automatically.
Turning on Flat View
You can turn Flat View on using the 
button on the default toolbar - right-click the button to see a menu of the different modes. You can also use the commands in the Folder / Flat View sub-menu.
Flat View modes
Flat View has three different modes:
- Mixed: Displays the contents of the current folder and all its sub-folders (and all their sub-folders, and so on recursively) as if they were all in the one location.
- Mixed (No Folders): Displays all the files in the current folder and all sub-folders as if they were all in the one location. Sub-folders themselves are hidden from the display.
- Grouped: Displays the contents of all sub-folders as a tree hierarchy.
The Flat View toolbar button cycles through these modes every time you click it.
Flat View folder format
From the Folders / Folder Formats page you can configure a format for Flat View (in the Folder Type Formats category). This is used automatically whenever you turn Flat View on. By default it's set to add the Location (relative) column to the file display.
Working in Flat View
For the most part you don't have to treat a Lister that's in Flat View mode any differently to any other - you can double-click, drag-and-drop, view, copy, and delete files in the same way you normally do. You can use drag-and-drop to move or copy files into nested sub-folders - you can even move files from one sub-folder to another in this way.
Drag and drop
If you drop a file into the file display - but not onto a sub-folder - then the base folder will be used as the target. Normally when you drag a file you can't drop it in the source folder - as this would be a no-op - but in Flat View you can do this, and one effect of this is that it can be easy to accidentally move a file from a nested sub-folder to the base folder without necessarily meaning to. You can always undo such operations, but it's worth remembering this is a possibility.
Copying nested files
The only real difference in file operations in Flat View mode comes when you copy files from within sub-folders (via drag-and-drop, copy-and-paste or using the Copy Files command). You can choose two ways of performing the copy:
- Recreate: Opus will recreate the source folder structure (relative to the base folder) in the destination.
- Same Folder: Discards the source folder structure - all files would be copied directly into the target folder.