While testing artrage, I missed many times this function. Be able to select some part of drawing from a transparent layer, and paste it on another layer.
dirty workaround : duplicate layer, delete part A let part B. back to first layer, let part A, delete part B.
It would be much easier if we just could select an area, cut, and paste somewhere else.
Beeing able to select and move stuff is also a great thing I missed.