@Anonymous
This is a preview feature and should be available directly. Can you try to update your expression as per below mentioned expression:
Launch( "http://bing.com/search",
{},
LaunchTarget.Replace )
If you do not have any parameters to pass, leave the second argument as is.
Note: This does not work in Edit mode, you can test it out in the Play mode after publishing the application.
Hope this Helps!
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