Cannot view 3D path. Please help!

I made a 3D path, but I cannot view it. I only see that red circle moving, following the blue rails. I did attach it to a camera. In every tutorial people activate 3D path by just selecting it in the layer properties window, but I cannot find this window. Where can I find this window? Is there a key combination to activate it? I use Toon Boom Studio 7.1. Thanks in advance!

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