Those scheduled transactions are latter occurrences of schedules. When you select it, it selects automatically the first occurrence of that schedule, which is the only one you can actually enter as a transaction.
This is by design.

So is it badly designed with respect to the export of the SQL database? I tried to do computations with scheduled transactions by saving the data (from *.kmy) to a SQL database and use the power of SQL queries.

In the table kmmSplits I find the first occurrences of scheduled transactions only up to the end of March 2013 (these are not all, some schedules have their closest scheduled transaction later this year). And these are not all transactions scheduled within that period of time (some schedules have lower frequency than others). Isn't it then confusing and pointless to put scheduled transaction into kmmSplits at all?

You can decide how many occurrences in the future you want to view. (or days, I don't recall exactly now)

Right, I can set the number of days to preview schedules in the ledger under Settings/Configure KMyMoney/Scheduled transactions. But I want the scheduled transactions that are shown in the ledger to show up also in the table kmmSplits after saving the data as SQL database. There I can find only the first occurrences within a fixed period of time, which is unaffected by the settings.

To KMyMoney, only the first occurrence really exists, the rest are just shown on the ledger as a "convenience"

There is a report for schedules, perhaps that suits your needs.

I couldn't find any report that gives all scheduled transaction within a certain time period. Exporting schedules to icalendar also gives only the first occurrences. It seems there is no way to export a list of scheduled transactions as shown in the ledger view.