You can manage your finances for multiple companies using QuickBooks Online (QBO), but each company requires its own separate, paid subscription, Christine.
As of now, QBO doesn't have a built-in function to automatically "split" an existing company file into multiple distinct files. Each QBO account is designated for one company file or business only. This helps to keep track of taxes and forms for each business.
I’m including this link to help you learn more about managing multiple company files in QBO: Create or add another company file to QuickBooks Online.
If your multiple business segments operate under a single legal entity and don't require separate tax filings, you can use the Class or Location feature available in QBO Plus and Advanced. This approach allows you to effectively separate and report on financial activity for each segment without incurring the cost and administrative complexity of maintaining entirely separate QuickBooks company files and subscriptions.
Please let us know if you have any further questions.