Can you give a time stamp on the video to see what you mean? Maybe a screenshot or some more context?
Perhaps you mean that there are two meshes inside the same object, in which case you can select the mesh you want to separate and P to separate by selection.
Adrian Bellworthy
replied
Can you clarify what you mean? You can't unlink a vertex, only as Omar said, P to separate, but that then creates a new object. You can unlink objects, but I don't think that is what you want, I could be wrong though... Enlighten us, please!
