From the top menu, select Edit > Preferences ( Windows/Linux ) or Harmony Advanced > Preferences ( macOS ).
Select the Layer tab.
By default, drawing layers have two art layers: Line Art and Colour Art. If your Support Overlay and Underlay Arts preference is enabled, your drawing layers will have four art layers: Overlay Art, Line Art, Colour Art and Underlay Art. For more information, see Enabling Overlay and Underlay Art Layers
In the Layer Drawing Options section, set the art layers to the desired art mode. Once this option is enabled, all new layers will follow these settings. It will not affect any existing layers.