Is there a way to filter or sort my iOS Apps by Account which was used to purchase them? Related to this question:

I have used several accounts to purchase/get for free a lot of iOS Apps. I'd like to sort them by account that was used to purchase them, since clicking through all those Apps with the Information Window is infeasible.

The problem I really want to solve is the following:

Sometimes, there are updates for apps purchased from other country stores (other accounts) - these show up in iTunes, but only as nonzero number next to the Apps Category.

E.g.: Today, if I use my main account (Austria) then I see no update notifications, but when I use my US account there is the number 3 next to the Apps category. I just want to find out what all the accounts are that I might need to check. (Yes, there are some that might have slipped my mind)
I've multiple accounts as well. I'd like to use free US apps as well that they don't provide on my countries App Store. Neat trick.

Anyway. Unfortunately there isn't a sort option existing in iTunes like the one you've asked since Apple won't care about our situation in general. Most users will only have a single account.

Also there isn't a third-party app for that.

So we're stuck with changing accounts all the time. But one advice that I can give you is that check some of those apps that you've downloaded with your US account in Austria store. Maybe those developers placed theirs apps in Austria store as well as of now. Deleting the old one and re-downloading it will keep your app library more organized.