Hello,
Every business is different, and it's important that QuickBooks Online gives you the flexibility you need in your bookkeeping. You can make tons of customization changes on your invoices depending on your needs. I'd be happy to explain how to add a column for duration on your invoices.
You don't have to upload a custom invoice from scratch. You can simply use the Custom Form Styles tool to edit the existing default template to include your column for duration.
Here's what you'll do:
1. Click the Gear icon.
2. Select Custom Form Styles.
3. Click New Style > Invoice.
4. Toggle to the Content tab at the top of the page.
5. Click the middle section of the invoice to edit.
6. Click EDIT LABELS AND WIDTHS.
7. Change the name of one of your existing columns to read: Duration.
8. Select Done.
That's all there is to it! Here's a screenshot for reference.
I hope this helps you get back on track. Let me know if you've got any other questions.
Cheers!