Let´s have a look how to copy concepts within one map or between individual maps.
to duplicate (copy&paste) existing concepts in one map, mark the desired concepts by mouse holding Shift key or click each of the concepts while holding Shift, then, press Ctrl+C. Afterward, click on an empty area on the map and press Ctrl+V to paste the concepts.
to duplicate (copy&paste) existing concepts between individual maps, proceed in an analogous manner. Mark the desired concepts, press Ctrl+C and then choose any location - new or an existing map - of the concepts.
Along with the concepts, the notes on the individual concepts are copied to the new location as well.
View video how to copy concepts: