It doesn’t seem to work for me at all unfortunately, although it looks correct in the UI Builder.
In game:
In editor:
<engine:UXML xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:engine="UnityEngine.UIElements" xmlns:editor="UnityEditor.UIElements" noNamespaceSchemaLocation="../../../../UIElementsSchema/UIElements.xsd" editor-extension-mode="False">
<engine:TabView view-data-key="Tab1panel">
<engine:Tab label="Tab1" view-data-key="Tab1tab">
<engine:Label text="Label" />
</engine:Tab>
<engine:Tab label="Tab2" view-data-key="Tab2tab">
<engine:Label text="Label" />
</engine:Tab>
</engine:TabView>
</engine:UXML>
What am I doing wrong? Using Unity 2023.2.19f1