In Windows > Editors > Canvas Layer Editor, choose Layer >Merge below, Merge visible, or Merge all.
After you have finished sketching on two or more image layers, you may want to merge them into a single image layer. After you merge two or more image layers together, you cannot split them into separate image layers.
If you merge a shape layer with an image layer, you will end up with a single image layer. All shape properties will be discarded. The image will still look the same, but you will not be able to edit the shapes as shapes.
To merge all image layers into a single image layer
All image layers in the canvas plane are merged into a single image layer.
You can undo the merging of layers by choosing Edit > Undo.