Hello Yeonjushin.,
Welcome to the Community page,
You will need to exclude all the transactions you have just csv into QuickBooks if you don't want the bank codes to show in the description section, you do this by ticking the little box next to date then exclude will highlight to click, this will remove them. then on the csv you need to put date amount and description on the csv, the description collumn can be empty and when you upload it into quickbooks and map it, it should not post your bank code in all of them.
Let us know how you get on.