Good to see you here in the Community, rockinraerenee.

Yes, you can create a statement for one project under a parent client in QuickBooks Online. Please be reminded that the statement will show the client's total open balance regardless if you filter its date for one project.

Here's how to create a statement for one project:
 

1. Go to Customers.
2. Locate your client's name and click Create statement.
   
3. Filter the statement date and hit Apply.
   
4. You can Print or Preview the statement.
   
5. You'll see the invoice and payment from the print or preview screen including the client's total open balance.
   

To know more about how statements work in QuickBooks Online, you can refer to this article: Create and send customer statements in QuickBooks Online. It contains information on what options you can include in your customer statements.

I appreciate your time working with us. If there's anything else I can help you with or other QuickBooks concerns, please let me know in the comment section. I'm always here to help. Have a lovely day!