Hi accounts-zorbasb,
The past entries were included in the migration process because they are part of your records. Even if you've inactivated some bank accounts, as long as they have transactions, they are still part of your records and therefore be included when you migrate to QBO.
On the other hand, the only way to delete transactions is to go to each of them individually.
You may consider Fiat Lux-Asia's suggestions to remove the transactions that you don't need. However, please note that deleted transactions will also affect your reports, so you'll want to keep that in mind, too.
On the other that, we have Help Articles for QBO should you need some references in the future.
Let me know if you have more questions in mind. Thank care, and have a good one!