I assume you're referring to this step in your rapid developer course?
https://academy.mendix.com/link/modules/79/lectures/659/2.8.3-Starting-a-New-Sprint
While it may no longer be called the planning tab (and this text should be adjusted – there will be space for feedback on the course at the end of the course, or you can send your feedback to academy@mendix.com) the screenshots in that step of the course show the correct places to be and how to finish your tasks, so you should still be able to progress.
After open Project Dashboard in TOC Planning tab is visible