Another new feature that is starting to roll out for Microsoft Project’s Project for the web is Copy Project:
Click the project name then on the project panel click the ellipsis in the top right corner, on that menu you will see the Copy Project option.
It looks like the rollout is not yet complete as the feature isn’t fully available on a few of my tenants but this will enable you to copy an existing project rather than starting from a blank canvas. See the roadmap item here for details: https://www.microsoft.com/en-us/microsoft-365/roadmap?filters=&searchterms=60591
Modern Work Management - Project and the Power Platform blog 