I need to undo something I did. I moved some transactions from one category to another and its thrown everything out. Help?

I've got you covered, info-rumbleinroc. Let's work together so you can undo those transactions seamlessly in QuickBooks Online. 

Since you already categorised those transactions, we can manually Undo them from the Categorised tab.

Before doing so, consider using the audit Log to keep track of those transactions so you'll have a guide before unmatching the transactions. 

Once you're ready, here's how to unmatch the transactions: 

1. Go to Bookkeeping, then select Bank transactions. 
2. Choose the tile for the bank or credit card account you downloaded the transaction.
3. From the Categorised tab, find the transaction you want to unmatch.
4. Select the blue transaction link in the Added or Matched column to see the matched transaction.
5. Click Undo from the Action column.

From there, we can review them and categorise them into the correct category or accounts. Here's an article you can refer to for more details: Categorise and match online bank transactions in QuickBooks Online. 

When everything is settled, you can visit this reference if you want to reconcile your accounts in the future to keep your books balance: Reconcile an account in QuickBooks Online. 

If you have any trouble with any transactions in QuickBooks, please let me know, and I'll do everything I can to help here in the Community.