That was just an old way of visualizing what your nodes were doing, but that has been discontinued. Now it makes all of that under the hood without you noticing, so do not worry about it, we have all forgotten that by now.
Adrian Bellworthy
replied
It was part of the node wrangle add-on, with the the add-on enabled the SHIFT+CTRL+CLICK added a viewer node and connected it as needed. Now the Material Output does it all without adding an additional node.
