Change material parameter in widget Animation

So I just finished the Unreal Fest tutorial here:
# Advanced UI Templating Techniques

in 20:06, there’s a animation bar which control the material parameters there.
But she didn’t told us how to setup that animation to control the material parameters.
And I couldn’t found it in my project.
Although I know other ways to control the parameter in Animation. I really struggle with her approach.
Anyone knows how?