I run 4 companies using Desktop Pro, not online. Will the new online version require a separate subscription for each company?

One QBO account is for one company file. Why don't you stick with QB Desktop to manage multiple company files?

I've got the answers you're looking for handling multiple companies, DBZ.

In QuickBooks Online (QBO), you can have as many companies as you'd like under the same account. However, each company you create requires an additional subscription, but you can access them with the same sign-in info. It lets you quickly switch between companies to manage everything more efficiently.

To add a new company:

1. Go to the QuickBooks pricing page and select the subscription you want. 
2. See a page that asks you to create an Intuit account to buy QuickBooks. Scroll to the bottom and look for the small text that says Adding a company to an existing account. Select Sign in next to this.
3. If signed in to QuickBooks, confirm the account displayed for the new company file and select Continue.
4. When asked, enter the same ID and password you already use for QuickBooks. 
5. Fill out all the information about your new company.

With multiple companies, you'll choose which one to open when signing in to QuickBooks Online. To switch between companies, click the Gear icon and select Switch company.

To learn more about managing multiple companies, check out the following link: Managing your companies.

Additionally, you can visit this page to learn more about the difference between QBO and QBDT: Compare QuickBooks Online to Desktop.

Let me know if you have other questions about managing multiple companies in QuickBooks. I'm always here to help. Take care.

@DBZ 

Yes, when using the Online version you pay per company. This makes it way more expensive than Desktop for customers with multiple companies.

Also, it's not new. The Online version is over 20 years old, feature poor, and showing its age and brittleness.