Hello Keith,
We're unable to create .txf file in QuickBooks Online. As a workaround, we can pull your data through reports and export them to Excel.
- Click Reports on the left menu and search for the report you need.
- Click the Export option (paper icon) and choose Export to Excel.
You can use this article for reference: How to Export Reports to Excel.
Then, you can search an Excel to .txf converter online.
Let me know if you need anything else.
