From the FAQ:

How do I add more than one item to the progress bar at once? You can't do this yourself. When Rarity detects two or more attempts simultaneously, it automatically adds two of those items to the progress bar.

Since the progress bars are already stored in a stack (table), we could allow users to push/pop (add/remove) items at will to therefore reorder the items or track anything they want in arbitrary order. So... the question is, will this be useful? I'm thinking after #6 is implemented this could be an idea worth revisiting.

If it turns out to not be useful, we should just remove the paragraph from the FAQ though.