Use the diagonal line on the toolbar to add a line to a dashboard. This line visually separates the components in the Preview / Viewer.

The appearance of the line view is defined in the Property Panel.
On the
Components toolbar,
select UI Line
and drag it onto a View.
On the Property Panel, select to define the line appearance.
On the Property Panel, select the Orientation property and select the horizontal or vertical orientation of the line from the drop-down list.
Save
your changes.