Ability to REVERSE an image in PhotoLab

If you mean the Geometry palette in PhotoLab 4, I don’t see the things you’re referring to.

I also bought DxO Viewpoint - is that where I should be looking?

If PhotoLab has a menu where you can rotate the image one way or another, that’s where I would expect to find this, but since I can’t find even a rotation adjustment, I’ve been using the “Horizon” tool to rotate images.