Mirror/Flip layer by image center

[Maestrorobertus]

The flip horizontal feature will use the middle of the selected layers. But I need very often to mirror layers from one side of the image to the exact other side. 

I haven’t found a way doing that else the with a little trick. I select my layers, do a copy. Then flip the whole image. Paste and then flip the image back. Doesn’t work with text, but for shapes its fine. 

So anyone knows a better trick?