I hope it's useful for some people.
In your video, you're in the Geometry Rollout and press the None-button, and pick a mesh. Even though, the mesh is not visible in the FP object and under Tree Editor it says 0 Items.
In my case, when I press None and then pick a mesh, I immediately see a point cloud of that mesh.
- What am I doing different from you?
Later, you explain "change to Tree Editor mode"
- What does it mean? In the video, you simply enter the rollout, but you're not pressing any button or changing modes.
In my case, I wanted to turn one single object to an FP object. InstanceToForest didn't work for me. The only thing it did was to reset scale and rotation of the picked object. Under Tree Editor, there were 0 Items.
However, when I had multiple instances, it worked, except it skipped the "original mesh" which appears to be the first mesh created, not the one I pick as source.
In your video, you picked one item, and when you pressed Instances to Forest, it turned them all, including the object you picked, to point clouds.