Hi there, jearn,
QuickBooks Online lets you remove companies you no longer use. To do so, you'd need to cancel those companies. They'll disappear from the list after 365 days.
There are just a few steps to get this done. Here's how:
Once done, an email will be sent confirming that we've canceled your subscription.I've added a quick video tutorial for your guidance with the process above.
You can also refer to this article: Cancel your QuickBooks Online subscription for more details.
Let me know if there's anything else you need. I'm always glad to help you out.