In addition to the support for line caps, a set of GUI elements for dashed line was introduced in the Strokes panel of the Freestyle Line Style tab.
By enabling the Dashed Line toggle button, you can specify three pairs of dash and gap lengths in the unit of pixels. Dash values define the lengths of dash strokes, while gap values specify intervals between two dashes. If a zero gap is specified, then the corresponding dash is ignored even if it has a non-zero value. Dashes are treated as separate strokes, meaning that you can apply line caps, as well as color, alpha and thickness modifiers. The image below shows a few examples of dashed lines on the default cube.
Panel (a) shows simple dashed lines along hidden edges. Panel (b) shows an example of dashed lines defined by two dash-gap pairs. Panels (c) and (d) illustrate dashes with round caps. Panels (e) and (f) are results of Along Stroke thickness modifiers applied to dashed lines.