SettingDefinitionList.addItem?

Official

Add-entry affordance. The framework renders a platform-appropriate control: on desktop, a + button in the list header (with name as the tooltip); on mobile, a tappable + {name} row appended below the list.

The mobile row is not part of the indexed items: it does not appear in search, does not receive delete or reorder affordances, and is not counted by onDelete/onReorder indices.

Since: 1.13.0