Tab Index and Accessibility

There's a small error in the "dispatchEvent" call. To use the "detail" property, you need to use "new CustomEvent()" instead of "new Event()" -- otherwise the "detail" property is simply ignored. e.g.:

        element.dispatchEvent(
          new CustomEvent("lut-tab-changed", {
            bubbles: true,
            detail: {
              relatedTarget: selectedPanel,
            },
          })
        );

https://javascript.info/dispatch-events#custom-events