Hi there, ladybum.
At this time, adding multiple projects to one invoice isn't possible in QuickBooks Online. However, while our engineers are working on making this a possibility, I'd suggest visiting out App Center. Here you can find a list of all third-party applications that allow you to have multiple projects on one parent invoice.
Heres how:
1. Go to Apps on the left panel.
2. Click Find Apps.
3. Type keywords in the search for an app field. (Such as multiple projects in single invoice)
4.If you find the App you'd like to download, click Get App Now.
From there, you can open the App and follow the in product help.
If you need further assistance, you can reach out here, day or night. Best of luck and have a wonderful evening!
