Thank you for attaching a screenshot, alshey. The option to set a default account in the Category dropdown from the Add resolving transactions isn't available. I'll elaborate on this matter.

QuickBooks Online simplifies your financial management by automatically entering certain details when you set up banking rules or when it recognizes the descriptions of your transactions. This feature helps save time and ensures that your records are accurate, making it easier for you to keep track of your finances.

However, it’s important to note that setting up default accounts while matching bank transactions or using the Resolve Difference feature isn't available. This limitation exists because default accounts are determined by the specific types of transactions you are handling (income or expense). Each transaction may require a different account based on its nature, such as income, expenses, or transfers.

In addition, I've added this article about organizing your accounts to match your bank and credit card statements: Reconcile an account in QuickBooks Online.  

Have questions about bank transaction management in QuickBooks Online? Feel free to drop your specific query in the comments below. Our team is committed to delivering precise, actionable solutions tailored to your unique accounting requirements.