I am trying to use and customize the UI5 SideNavigation web component for levels of more than two. But I can’t make more than two levels.

I already tried adding three levels, but it failed.

<ui5-side-navigation>
  <ui5-side-navigation-item text="레이아웃" href="/layoutType" icon="bar-chart" expanded>
    <ui5-side-navigation-sub-item text="sampleLayoutType1" href="/sampleLayoutType1"></ui5-side-navigation-sub-item>
    <ui5-side-navigation-sub-item text="sampleLayoutType2" href="/sampleLayoutType2"></ui5-side-navigation-sub-item>
    <ui5-side-navigation-sub-item text="sampleLayoutType3" href="/sampleLayoutType3"></ui5-side-navigation-sub-item>
  </ui5-side-navigation-item>
  <ui5-side-navigation-item text="연습2" href="/practice2" icon="bar-chart"></ui5-side-navigation-item>
</ui5-side-navigation>