You can create various Teams Tabs for different projects on your site(s). Each project does not have to be from the same site.
To add Teamwork to Microsoft Teams, select Apps from the bottom left of the navigation bar.
You can then search for Teamwork within the Apps area. Click the Teamwork card to select the app.
Once selected, click Add and choose Add to a team from the dropdown menu.
You will then be given the option to create a Teamwork projects tab or a Spaces tab.
Click Connect with Teamwork to login to your Teamwork site.
Once you have successfully entered your login details, if you have multiple Teamwork accounts you will be able to select which site to login to.
You will also be required to allow third party access to your data to continue.
It is also possible to connect via the Apps subsection when viewing an individual team profile.
For more information, see: Linking a Project to Microsoft Teams