You can get the wanted result by copy the frames from one layer and the paste the frames on another layer.
1. Select all frames in the layer by clicking on the layername.
2. Choose Edit > Timeline > Copy frames.
3. Select the layer you want to paste to or create a new empty layer.
4. Choose Edit > Timeline > Paste frames.
To fix the pasting off center, hold SHIFT when pressing control+v (SHIFT+CTRL+V), or alternately highlight the frames in your timeline, right-click and choose 'Copy Frames', go to a new layer, right-click and choose 'Paste Frames'.