Hello Laura,
Thank you for reaching out to the Microsoft Community. My name is Seun and I'm happy to help.
I am sorry that duplicating a Microsoft Teams team in the new version is not directly available, however i can suggest some workarounds.
Open Microsoft Teams. Click on Teams in the left sidebar. Next, click on Join or create a team and then select the Add people to team button at the bottom of your teams list. Click Create Team. In the creation window, select Create from…, then choose Team. You’ll see a list of teams that you currently own. Choose the team you want to copy. Name your new team, add a description, edit the team privacy, or edit the team’s data classification if your organization has set this up. Use the check boxes to pick which parts of the team you want to copy: channels, tabs, settings, apps, and even members. When you’re done, click Create.
I know this may not the perfect steps you are looking for, but they can be helpful. You can use the feedback link below to report the issue to the Microsoft Developer Team at:
https://feedbackportal.microsoft.com/ and they will put features like this into consideration for future updates.
Thank you for your patience and understanding,
Best Regards, Seun