If you click Add under the Action column, this will add the transaction to your register. Let me show what happens if you do this.

You can select this action to add your transaction to your register if you don’t need to add any transaction details or monetary splits between accounts or jobs. Please see the attachment below for a better reference:

You can refer to this article for more details: Find, categorise, and edit transactions in QuickBooks Online.

I'm also adding this article to guide you on how to reconcile your account flawlessly: Reconcile an account in QuickBooks Online.

Feel free to drop by the Community whenever you have further concerns about your transactions. Have a great day ahead!