Good day, lrhmail451.
I'm here to answer your inquiries about the process of categorizing transactions in QuickBooks Online (QBO).
There's no need to delete something after you categorized it in QuickBooks Online (QBO). Once a transaction is categorized, you can't use it again unless you undo or unmatch it. Check out this article for more details: Unmatch downloaded bank transactions or move them to another account.
Here's an article to learn more about matching and managing your downloaded transactions: Categorize and match online bank transactions in QuickBooks Online.
You can also open this link for additional reference about managing your income and expenses in QuickBooks Online.
For additional resources about managing your banking transactions, you can check out the topics from this link: Find help with bank feeds and reconciling accounts for QBO.
Let me know if you have other questions about categorizing transactions by leaving a comment below. I'll get back to you as soon as I can.