eog-multiple-save-as-dialog.ui still used GtkAlignment and the action_area which are both deprecated.
I also wanted to add the use-header-bar property since now all the dialog have the buttons in the headerbar, but I didn't know what to write in the title (both the title and one of the button has the same "save as" label).
If you have any suggestion, I will made the appropriate change.
Thanks !