copy paste on transparent layer

[denzjos]

rich, I know how to copy and paste but I want to know if there is an easy way to copy and paste on a transparent layer so that the result is the same as on a normal layer : the pasted information hide the underlying information (if the layer mode opacity is set to 100%). On a transparent layer the colors are added with each other, not replaced by the pasted information. this is normal because the layer and copied information are on a transparent layer. My question was if there was a possibility to paste something from a transparent layer on a drawing that exist on a transparent layer in the way that the pasted layer is replacing the existing information (not adding). And doing this in a simple way (little manipulations). 
PS: about the knot, Alexander the Great had a solution 

A dummy example : 

  dummy.xcf (Size: 104.7 KB / Downloads: 226)