Open the Save as File List command from
the File > Save Image Set menu and
from the main
toolbar using the 
button's drop menu. .
Save as File List
The Save as File List command saves the names of images in the image set to a File List, or "axf file". The same image set can then be opened later by opening the .axf file. This command does not save the images to files. If you have changed the images and want to save the changes, use one of the other commands that save the image set, such as Save to Folder (Ctrl+F).
Open the Save as File List command from
the File > Save Image Set menu and
from the main
toolbar using the button's drop menu. .
In the dialog below, notice that the Save as Type field has only 1 entry, Mira File List (*.axf). In this example, the file will be saved as a file named "new file list.axf".
Save All, Save to Folder, Save with Suffix, Saving Image Sets