The important thing is the points attribute. It is a list of coordinates, relative to the x and y coordinates of the slider. This list of coordinates is put together to a
bezier curve.
The list has to be set in the following format: (x1,y1),(x2,y2),...,(xn,yn) for a slider with n points.
If you want to create a simple left-to-right slider that is 100px wide use the following value for points: (0,0),(100,0)
You'll see a preview of the slider shape in the editor (the red line).
I think you can figure out the rest by yourself.