With this feature you can change the title for the selected images.
To rename multiple captions at once you need to select them first. After you have selected your images, select “Collection | Operations | Rename Caption”. You can also press the keyboard shortcut [F2].
Here you can enter the new caption that should be applied to every selected image. The headline will be applied to the Image Details (XMP/IPTC) as well. You can check this by typing [Alt]+[Enter] to see the changed headlines in the Image Details pane.