Flip Clef

How do I reverse the key and key signatures like this with Dorico 5?

There are turned and reversed clefs in Bravura which you can add as text and reposition. If you’re recopying a crab canon, I would use a mirrored clef and key sig rather than these turned ones. (It’s not Tafelmusik, meant to be read literally upside-down.)

If you have Dorico Pro, see this post to achieve a result like this: