Sorry, nesting container accounts isn't possible. We don't want to complicate things so we decided one level of container was enough to hide any private information such as employee names etc from the financial reports.

We'll have a look into your other question about performance tomorrow, we haven't tested the system to this level. Also on the Mac, there isn't a filter that filters down the list of accounts like there is on the iOS version. This might be rather more important given the many thousands of accounts you're proposing.