IntellIJ IDEA needs a new Full Screen mode

I found a little bit problem with the "New UI" design in the Android Studio Canary version, (it is based on the last IntelliJ IDEA). Full-Screen mode works well, but it looks like an old design style when the toolbar was built in one line. I consider that in the new design of idea, we don't need to use the toolbar in full-screen mode, because it is already hidden in one button. On the first screen all is fine, it shouldn't be hidden in full-screen mode, it already looks like it, in the full-screen mode we just need to hide the Windows panel (On Windows OS). But instead of this, in full-screen mode, this button (the hamburger button, I use custom icons, so my button looks quite different) is hidden, and I must use this ugly toolbar from the old design.
And on the last screen, the current version of the toolbar for the new UI style. Why do we need it if we already have one button, where we can find all this?