This comments is about why is it not possible to see or turn on Levels in the Revit Project file as it is in Families and project files in Vasari? That is really a thing I am missing when modeling, especially with massings. For me it is littlebit strange that is not possible when it is a tool that works with objects that almost all the time have relations to Levels. It makes it more difficult to work in 3D with the object modeling.
I also think that it will be a good option to can visualize all Levels in 3d ....
Anyway you can make visible them, but only one at a time, setting the Work Plane to one of the Levels and then clicking on Show....
It is a little workaround but not really good. Lets hope some from Autodesk sees this post and implement it soon 🙂