How can I edit the Case entity ribbon to add a button?

How can I edit the Case entity ribbon to add a button?

I'm referencing the step in Figure 26.9 from the book Microsoft Dynamics Unleashed 2016.

I need to add the Button highlighted in the picture.  However, I have a big constraint. I can't use RibbonWorkBench.

Is there any tutorial that will teach me how to add the button to the Case entity ribbon without using Ribbon Work Bench?

Thank you!