Can I reset the journal number to 01 at the start of a new fiscal year?

Yes, resetting the journal entry numbers is made possible in QuickBooks Online (QBO), kidsshangrilahom.

We can turn on first the Custom transaction numbers feature in QBO to get control of the auto-populating number of your journal entry. Here's how:

1. Click the Gear icon (⚙) on the top menu and choose Account and Settings.
2. Go to the Sales tab.
3. Select the Sales form content section and check the box to enable Custom transaction numbers. 
4. Press Save and then Done.

Once done, we can manually change or assign the entry numbers in the designated box in the program. Whenever you create a new one, the system automatically increases it by one based on the last number entered. Let me guide you on how: 

1. Click +New and choose Journal entry.
2. Choose the recent arrow button in the upper left corner. Then, open the entry you want to edit.
3. On the Journal no. box, manually change or assign a number. You can add letters together with numbers.
4. After making the necessary changes, hit Save.

I'm adding this article to help you update or correct your entries: Reverse or delete a journal entry in QuickBooks Online.

I'll be a post away if you have follow-up questions about managing journal entries and other transactions in QBO. You have a good one.