new variable

To show the value of a variable, insert a reference into the text. That can be done by clicking the Insert Reference button.

In the example image above, there is a Text variable called "Scene_Name," and it has a default value of "Scene 1: Introduction."

A variable will keep its value until a trigger adjusts it. After the value is adjusted, all of the references will show the new value. 

• If you want a dedicated text field to show the current scene name based on one variable, you would need triggers to adjust the variable on every slide the user where the user might "enter" the scene. For example, if the built-in Menu is available, every slide in a scene would need a trigger that adjusts the variable to the name of that scene. 
• Alternately, you could use different variables for the names of each scene. 

Here's a tutorial about variables that might help you: Getting Started with Variables in Storyline 360 - Articulate 360 Training 

How strange that there apparently is no built-in Project.SceneName variable, when there is one for the scene number, as far as I know. I could see that being useful for writing slide templates that include the name of the scene, for example as a chapter intro slide.