An error occurred while saving the commentAdam commented
Attached is an example of how InDesign currently exports the spine marks. You can see they are shorter and sit further away from the trim than the outer marks. I realize this is to indicate they are not trim marks but they are really not helpful when you are exporting a cover spread. It would make more sense to me for them to not show up at all on the spine, to show up the same size as the outer marks, or to have an option to make fold marks on a page that you designate as the spine.