1. add second, third sort by. when click "sort by level", items sorted by level then click "sort by rarity", items sorted by rarity, but should secondly sort by level, then click "sort by power required", items sorted by power required, but should secondly sort by rarity and thirdly by level, This is imported when have large collections of cards. 2. add API or (export to csv?) to export self's collection.
There's already a kind of API for extracting your item collection. There are also many tools for analysing the collection, graciously created by Neoncat. See here: http://forums.cardhunter.com/threads/utility-neoncats-list-of-tools-extras.5743/
Even as someone working on a utility that primarily sorts and filters items, I'd still like to see the in-game interface for this improved. A console command to directly export collections to the clipboard would also make it much more convenient for players to analyze their hoards and help justify the creation of more advanced tools for this purpose. It's probably also worth mentioning that @neoncat's tools are now hosted online here: http://www.stexe.com/neoncat/
I second this proposal. They way it is implemented right now is not really useful, since items are sorted by name once you group them by rarity or power required