This is an example of destructive interference, where a crest and trough meet and temporarily cancel each other out before continuing along the slinky.
In this scenario, two crests meet on one point in the medium to create a singular wave and then go back to their original shape and size.
Like in the other videos, there are two sources of waves interfering with each other. But because they have the same amplitude and wavelength, the pattern appears to stay in place through specific points. These points, “nodes”, can be seen as parts of the slinky that don’t move.