I've noticed a few problems with Collections as Parallel Resources:
1. Sometimes not all resources are present in the drop-down list when clicking the "parallel resource list" button. For example, I have "Topical Bible" Collection including New Naves Topical Bible, Nelson's Topical Bible, New Topical Textbook, and Dictionary of Bible Themes. All are type:monograph, and indexed to the key english word. BUT for some reason, Dictionary of Bible Themes is not included in the drop-down list, even though it is part of the collection. Interestingly enough, if I open Dictionary of Bible Themes, I can "arrow" to the other three resources, but once in any of the other resources I can't arrow back to the Dict of Bible Themes, since the it is not visible in the drop down list.
2. When I make a collection of "type:monograph" resources, and click the option to "Show in Parallel Resources", it doesn't work. After I make the collection, when I open one of the resources in the Collection, there is no "Parallel Resource List" button to display the drop-down list. For example, I made Collection of my "Church History" monographs, so I can easily open my favorite parallel resources, but it doesn't work. I think this is because the resources are indexed by "page number" rather than verse or some other data type, BUT there should be no reason why we can't specify these Collections as Parallel Resources too. True, you can't "arrow through" the resources, but you can easily select the similar resources and open them. This saves going to the library and searching each time, and is a valid and helpful way to use collections. It would be nice to be able to set ANY Collection (even those including resources of different types) as a parallel resource set.