Howdy michaelalbee,
I see what you want to do there. The photo view uses the JS Isotope library. Even if you inserted the <hr> elements, best case they change nothing, worst case they completely mess up the view.
You are going to either want to customize isotope’s settings, or strip isotope out and replace it with your own concoction. You can effectively strip it out by switching to Skeleton styles.
I wish it could just be an easy <hr> insertion 🙁 . But, the isotope library does a lot more than keeping things aligned. It also does a great job of making the photo view responsive. The only draw back is that it is not easy to modify how it functions. Sometimes it is best to just strip it out and build your own if you want to change the layout.
Does that all make sense? What did you decide? Please let me know. Cheers!
– Brook