Using tags feature for journal entries in QuickBooks Online (QBO) isn't possible, financedept.
However, we have a workaround that you can utilize. I'd be delighted to walk you through how.
You'll want to use the class tracking feature if you're using the QBO Plus and Advanced versions. But beforehand, you'll have to turn it on first. Then, add a new class. Here's how:
Go to the Gear icon, then select All lists.
Choose Classes.
Click New. Give this a class name.
To add a sub-class, select Is a sub-class and select the main class. You can nest up to five classes.
Hit Save once done.
Once you're all set up, you can record journal entries with classes. For more details about creating this, you can check out this handy reference: Create journal entries in QuickBooks Online.