Lightroom Desktop: How do I create a diagonal watermark?

This isn't actually possible yet. We've asked the document team to correct the image showing the tools current design limitation. Apologies for the confusion. 

Darn - That was the answer I suspected but not hoping for.
Don't you hate it when your marketing/doc team doesn't use the actual product to make the visuals for the release notes/launch materials?  (Rhetorical question as a former corporate marketing guy)