Follow these steps to create lines in Design.
Create a new geometry or edit an existing one to enter editing mode.
In the design tool, you can now create lines consisting of one or more points. As default will the Line tool be selected under TOOLS.
Click at a desired position in the scene for the first point and continue clicking to define points in the line segments. You can also specify a height via SNAP - Height, but this must be done before the point is created in the line segment. If you want to snap on a visible model in the scene use SNAP - Asset.
To delete a line segment, point at the segment and right-click - Delete line or use the shortcut Delete.
To finish an ongoing line segment, press Esc or right-click and choose End line segment.