You'll be routed to the Expense screen in QuickBooks Online (QBO) when clicking on the Edit button. This helps change something in the grayed-out sections and make additional changes.
Though, you can always edit the transaction directly and click on Save once done. I've attached a screenshot for reference.
Let me share this article that you can learn how to add transactions directly to an account register.
You can leave a comment below if you have further questions. We're always around to help. Have a good one.