Hi there, @frostieg. 

Glad to know about your plans of moving over to the QuickBooks Online Plus version. 

Sure, I can. Every company you'll add will be a separate paid subscription. Visit the QuickBooks pricing page to compare the price and features, then select the subscription you want. 

I'm also adding some of our helpful articles that you can use as a reference. Read through these topics: 

• Sign in to multiple QuickBooks Online companies with one user ID. It'll guide you in the right direction of using the same credentials to all of your QuickBooks accounts. 
• Create or add another company. It has a step-by-step guide in adding multiple companies to your QuickBooks Online account. 
• Move your QuickBooks Desktop file to QuickBooks Online. It helps you learn about moving your QB Desktop files should you finally decide to move over to Online. 

Let me know if there's anything else that you need. I'm always around to help you further.