Avoiding setting defaults multiple times for nested objects can be achieved by setting the defaul...

Schema.Struct({
  background: Schema.optionalWith(
    Schema.Struct({
      dotColor: Schema.optionalWith(Schema.String, { nullable: true, default: () => 'var(--x-flow-bg-dot-color)' }),
    }),
    {
      nullable: true,
      default: () => ({
        dotColor: 'var(--x-flow-bg-dot-color)',
      }),
    },
  ),
})