Good to see you here in the Community, NelsonDFS.

Let me share a little information about adding a line item number in QuickBooks Online.

As MaryGraceS referenced, you'll need to manually add a number column to identify the line items on your estimates since this isn't currently offered in QuickBooks Online. I can definitely see how this feature would be useful. As a team with a massive road-map, we have to pick new features based on the value they’ll add to the most users possible. I recommend sending this request straight to our product engineers through feedback.

The Product Development Team is constantly working to improve QuickBooks and make it even better for you as the customer. I'll share your feedback with them to let them know about the changes you'd like to see made.

For additional assistance, feel free to reach out to our Customer Care Team. Agents will be able to assist you further in getting this resolved quickly.

Drop me a Reply if I can do anything else for you. Have a great rest of your day.