How do I open a QB portable file using QuickBooks online?

You can use the trial version of QB Desktop to open the portable file (*.qbm).

Portable company files are great for sharing or moving accounting data around when you don't need a full backup. I'll provide further details on this matter.

The feature to open portable files within the program is unavailable. However, you can create and open portable company files using a QuickBooks Desktop trial as a workaround. 

To create a portable company file in QBDT, follow these steps:

1. Log in as an admin and open QuickBooks Desktop.
2. Click on the File menu and select Create Copy.
3. Select Portable Company File and click on Next.
4. Give your portable company file a unique name to distinguish it from your regular company file.
5. Select a location to save your portable company file. Choose a location that's easy to find, such as your Windows desktop. 
6. Click on Save and then OK.

Once done, you can then send it online or save it on a USB drive.

Check out this article for detailed information and instructions: Create and open portable company files in QuickBooks Desktop.

I also suggest looking for third-party apps to integrate with QBO to manage portable files. Find one through this link: https://quickbooks.intuit.com/app/apps/home/

I'm here to help you with questions about working with your QuickBooks Online company file. Reach out to me by hitting the Reply button below. I'm looking forward to assisting you.