Replacement management for items of same type

Wildlyfe

I am having trouble figuring out how to make this work. It doesn't seem to matter which setting I select. For example, I want to be able to swap out the unicorn horns from the Millennium Horse bundle instead of having to delete/import each time I want to switch between them. I have all the horn props with the same "type"in the database editor. Does it not work for props? They are set as "attachments" also - not sure if that matters. Anybody know?