ArcGIS Pro 3.4 API Reference Guide
ArcGIS.Desktop.Mapping Namespace / UniqueValueRendererDefinition Class / UseDefaultSymbol Property
Version

UseDefaultSymbol Property (UniqueValueRendererDefinition)
Gets or sets a boolean to indicate that DefaultSymbol will be used to draw features whose values are not found in the values list.
Syntax
public bool UseDefaultSymbol {get; set;}
Remarks
You should use this when there are more unique values that what you set as ValuesLimit.
Requirements

Target Platforms: Windows 11, Windows 10

ArcGIS Pro version: 3 or higher.
See Also