Can I add another LLC on my QB account but account separately....Same owner different companies.?

Yes, it's called buying a second subscription. Because each LLC has a unique FEIN you cannot (in my opinion) get away with separation of entities by Class Tracking within a single company file. The IRS also says each company has to have separate books.

https://quickbooks.intuit.com/community/Help-Articles/Create-or-add-another-QuickBooks-Online-compan...

Create a new QuickBooks Online company

Here's how to create a new QuickBooks Online company:

1. Go to https://quickbooks.intuit.com/choose-country/.
2. Choose your country to be directed to your region specific QuickBooks Online website.
3. Select the QuickBooks Online version you need.
4. Choose to buy now, or start a free trial. (Note: This is not a UI-specific step, the "Buy Now" and "Free Trial" buttons vary depending on country.)
5. On the signup page, select Sign In or Add another account if you have an existing QuickBooks Online account. If you don't, continue creating a new one.

---

@john-pero wrote:

Because each LLC has a unique FEIN . .

---

A single member with no employees does not even need a FEIN, so you can have multiple such entities with the same SSN (or I don't see why not even FEIN), although I don't see what the point is because all the assets would be at risk; you may as well just be a SP with multiple DBAs.  In which case it is fine to use Class

https://info.legalzoom.com/llc-need-ein-4497.html