The duplicate manager lists all versions of the current darkroom image with their preview thumbnails. Hold down the left mouse button on a thumbnail to temporarily show that version in the center view. Double click to switch to this version and edit it.
The buttons on the top-right allow you to create new duplicates of the current image. You can either create a ‘virgin’ version (with an empty history stack) or an exact duplicate of the current image. For your convenience, you can also assign a name to each version.
The displayed name is stored in the version name metadata tag, which can also be edited within the metadata editor module.