defaultFillExtrusionLineWidthAsExpression

If a non-zero value is provided, it sets the fill-extrusion layer into wall rendering mode. The value is used to render the feature with the given width over the outlines of the geometry. Note: This property is experimental and some other fill-extrusion properties might not be supported with non-zero line width. Default value: 0. Minimum value: 0.

This is an Expression representation of "fill-extrusion-line-width".