Q: I bought the Collection Management add-on, when I reinstall the app, do I have to purchase the add-on again?
A: You do not. You can either use the "Restore Transactions" button, or alternatively, if you purchase the collections add-on from Apple, you will not actually be charged. The collections add-on is a non-replenishable purchase, so it can be redownloaded anytime. You can read more about in-app purchases
here.