In Unity 2020.2, we introduced several new features in Shader Graph that improved the workflow for artists. For example, by refining the user experience overall and introducing the Graph Inspector, Graph Editor performance has been greatly improved. As the end point of the Graph, the Master Stack is now a modular collection of feature blocks, replacing the monolithic Master Node.
The Master Stack is the end point of a Shader Graph that defines the final surface appearance of a shader. It helps users visualize the relationship between operations that take place in the vertex stage and the fragment stage. With Unity 2020.2, the Master Stack replaces the Master Node of earlier Unity versions. Read More technology | Unity Technologies Blog