VBA Chart Border: Line Join Style

How do you tell a Chart Border to have the Join Type "Miter"?
I've recorded a macro (several), but this piece of info doesn't show up?

With ActiveSheet.Shapes("Chart 1").Line
    .Visible = msoTrue
    .Weight = 10
    .ForeColor.ObjectThemeColor = msoThemeColorAccent6

How do you integrate this:
.JoinStyle = LineJoinStyle.Miter

I started of with Jon Peltier's "Resizing and Moving Excel Charts with VBA":
https://peltiertech.com/Excel/Charts...oveAChart.html
Thank you, Jon!

Then I recorded a macro for color and weight of the line, but I can't figure out the joint type/style.