Thanks for bringing your question forward here in the Community, Lizaluuu1.
I'm happy to provide some info about customizing reports in QuickBooks Online.
You can access the customization area of the Transaction Detail Report by clicking the "Customize" button in the top right corner of the page. Here you'll be able to access the Filter option where you can check the boxes for Vendors and/or Customers.
The following article provides additional info about customizing reports in QuickBooks Online.
If you need further customization options, you may consider submitting feedback to the Product Development Team for review. This can be done directly through your QBO account by clicking the Gear icon and choosing Feedback.
Please feel free to drop a comment below if you have any other questions or concerns. I'll be here to help in any way that I can.