Can you merge more than one invoice

Congratulations on publishing your first post here, @dbgjoinery. I'm here to address your question about merging invoices.

I can see how convenient it is to combine invoices or any other types of transactions. However, this is currently unavailable. Thus, I recommend sending your suggestion to our product engineers. 

Here's how:

1. Go to the Gear icon in the upper-right corner.
2. Under Profile, select Feedback.
3. Share your request and click Next.

Visit this link to check its status: QuickBooks Online Customer Feedback.

As a workaround, you can add the details from one invoice to another, and then delete it so it will not become a duplicate. Using a third-party app can also aid you.

See this helpful reference to learn about personalizing and adding specific information to your sales forms: Customise invoices, quotes, and sales receipts in QuickBooks Online.

Bookmark this article for future guidance in receiving customer payments: Record invoice payments in QuickBooks Online.

Please don't hesitate to let me know if you have any other questions about managing invoices. I'll be here to answer them. Have a great day!