As promised in our announcement for the new simplified course, we have added an ability to switch between the traditional and simplified courses. You can access it from the application settings page.
We have more details on how it works in our course switching documentation page. As stated there, it is best to pick one course and stick with it long term. Unsure which course to pick? You can make a thread in this forum about your goals and motivations for learning Chinese and we can help advise.
Next up on our list are various improvements to the review and lesson quizzes and surfacing more data to you on the dashboard to give you an idea of your progress.