Hey afrlme,
First of all, thanks for such a quick response!
I think I need to clarify that these animations are not for the specific slots in the inventory, but for the entire inventory background. So I'm not sure whether I'd want to use the animation section inside of the item section in the editor here? And yes, it is a looped constant animation for whenever the inventory is shown.
It's particularly strange because I've deleted the background image in the settings for the inventory interface, but it still pops up in the editing window.