Hi Kori. This is available today through Project for the web (see the help article: https://support.microsoft.com/en-us/office/move-your-project-from-project-desktop-to-project-for-the-web-143ab391-002e-451a-aedb-3b6fa1f6ab8b). We don't have the import capability in the new Planner app directly, but once you've imported a plan through Project for the web, you should be able to access it through the new Planner app. Thanks.