API Reference > imodeljs-frontend > QuantityFormatting > CustomQuantityTypeDefinition > primaryPropEditorSpecs primaryPropEditorSpecs primaryPropEditorSpecs: undefined | CustomFormatPropEditorSpec[] An array of specifications that are used to generate a label and editor in the UI used to display and edit the FormatProps. UI items defined as primary will be shown higher in the list of UI components. Defined in core/frontend/src/quantity-formatting/QuantityFormatter.ts Line 147 Last Updated: 12 June, 2024