seriesDashStyle

Specifies the line style of the series. May be:

Solid
Solid
ShortDash
ShortDot
ShortDashDot
ShortDashDotDot
Dot
Dash
LongDash
DashDot
LongDashDot
LongDashDotDot

Defaults to Solid.

seriesSettings: {
    spline: {
        seriesDashStyle: "ShortDashDotDot"
    }
}

This setting is demonstrated in the following example.