Windows PC? If so, i have found an application called Beacon. Its a download and install application, you go through all the catagories and check the things you want to add and remove from drops. At the end you export and it gives you the custom auto generated code to add into gameuser, game, and engine config files. Ive used it to add a few simple things here and remove a few there. So far its work flawless, I really havent went as far as making completely custom drops. However from what ive seen, i have no doubt it will work.