The Comment Keywords command finds all the COMMENT keywords in an image header and lists them into a Text window. If the Image window contains an image set, the current image or the image set may be listed according to the status of the Process Image Set flag, or button.
This command is executed from the Edit > Image Header menu.
The example below shows the COMMENT keywords from 2 images. Note that the ".txt" extension is automatically appended to the window title after the contents are saved to a file.
FITS Header Editor, History Keywords, WCS Keywords