I hope you're having a great day. Allow me to provide some more info on pledges and invoices.
Pledges are just like Invoices, so they'll go into the account you assign them to when you create one. The Invoices and Pledges go under the sales tab to keep track of the sales that happen in QuickBooks. Invoices typically contain items someone sales, so a pledge is set up to reflect that too. This is why they show up in a sales account.
I'm only a comment away if you have any other questions. Enjoy the rest of your day!