I have an estimate that is 280 lines long, I selected it to invoice only 5 items from it and the invoice is 280 lines long with 275 lines blank.

Thanks for reaching out to us, @KS1966.

I'm here to give insights on how to turn your estimates into invoices in QuickBooks Online (QBO).

Currently, there is no way to batch remove the line items that appear on the invoice when converting from the estimate. And I can see the hassle of going through all the items to manually remove it. While the feature you're looking for is unavailable, I'd recommend submitting your feedback to help improve the program.

To send feedback, follow the below steps:

1. Go to the Gear icon at the top.
2. Select Feedback.
3. Enter your comments or product suggestions. 
4. Then select Next to submit feedback.

To be updated with the recent and upcoming changes for QuickBooks products, visit these sites:

• QuickBooks New Features and Innovation
• What's New in QBO?

To know more about how an estimate works and convert it to an invoice, you can visit this resource for more information: Create and send estimates in QuickBooks Online. 

For future reference, check out this article to learn how to receive invoice payment in QuickBooks Online. 

If you need anything else, please let me know. I want to help in any way I can.

Thanks!  I appreciate your response and I followed your instructions on the feedback.