Here's a little hack to allow you to move the image on an individual layer.
It takes time and effort, but if you HAVE to do it, then this will work.
It's VERy roundabout. But hey.
1. Make the layer you want to shift the only visible layer in the pic.
2. Export it as a PNG file. It's lossless, so when you bring it back in later, it'll still be the same pic.
3. Set all your other layers to 'visible'.
4. Now, CLEAR the layer that you just exported.
5. Select that layer.
6. Import a tracing image. Yup... you guessed it... the tracing image is the old layer.
7. Now, EDIT the tracing image. You can resize it, and you can shift it. Unfortunately, you can't rotate it. (You will need to rotate the PNG file in another app if you need rotation.) Once it's in place...
8. 'Convert the tracing image to paint' on the selected layer (the one you cleared).
9. Now switch the tracing image off, so that you don't have it as an ever-present pasty film. And you'll be able to see if your layer shift is right.
10. If the painting looks good at this point, you can clear the tracing image. If you need to shift it a little more, just clear that layer, edit the tracing image, shift it to your heart's content, and convert to paint again.
I know this is long-winded, but it is a workaround. I would REALLLLY like a rotate function in there. But hey.