As I see me more as a tester of banks and credit cards, I do have a lot of accounts at several banks inlcuding their credit or debit cards and including individual (often high) credit limits. I need Excel to manage all these account and credit card numbers.
I can see all of them (except Fidor, but N26 although never agreed) under "meineschufa.de" and this is why I can see my current Schufa score: 95 from 100
I would say my behavior hasn't killed my score so far, but to be honest I don't really care anymore. I am 50+ and sure that I won't need any credit at all. I have no debts.