$ grep -r "preview in image" . | grep -v po ./plug-ins/jpeg/jpeg-save.c: gtk_check_button_new_with_mnemonic (_("Show _preview in image window")); $
$ grep -r "preview in image" . | grep -v po ./plug-ins/jpeg/jpeg-save.c: gtk_check_button_new_with_mnemonic (_("Show _preview in image window")); $
So the next step is to edit jpeg-save.c and find that line.