You can use a Keyword Node to create a static branch in your Shader Graph that references a Keyword on the Blackboard. The appearance of a Keyword Node, including its available ports, changes based on the Keyword it references.
Creating new Keyword Nodes
Because each Keyword Node references a specific Keyword, you must first define at least one Keyword on the Blackboard. Drag a Keyword from the Blackboard to the workspace to make a Keyword Node that corresponds to that Keyword.
You can also right-click anywhere on the workspace, and use the Create Node menu to make a new Keyword Node. Under Keywords, there is a list of Keywords that you defined on the Blackboard. Click on a Keyword in that list to create a corresponding Keyword Node.