Instead of adding a new subscription, you may be interested in the Projects feature in QuickBooks Online. According to the overview, "Projects is similar to job costing because it helps you organize all the pieces that make up a project. It includes transactions, time, and running reports so you always know how your project is doing."
Here's how you can turn on Projects:
1. Click the Gear icon in the top right corner.
2. Select Account and Settings.
3. Choose the Advanced tab.
4. Click the small pencil icon on the right in the Projects section.
5. Place a check in the box beside Organize all job-related activity in one place.
I'm trying to set up online version and i can't figure how I can add different companies, since I work for a construction company and each project is like a new company?
If you need to setup an actual different company file for each company, then you would need a separate subscription for each company.
If each project generates income for you but you work for only one actual company, it sounds more like you would want to setup each project as a separate customer that you get income from, or if you are using QBO Plus, you can setup each project as an actual "Project"
If you want more insight or help understanding how QB handles this type of situation, please respond back to this thread.