Whole cells can be copied to the clipboard as well. To copy a whole cell, select the cell in the hierarchy browser (make sure the focus is in that window) and choose "Copy" or "Cut" from the "Edit" menu. To paste such a cell into a target layout, choose "Paste" from the "Edit" menu.
Two copy modes are provided: deep and shallow copy. When "copy" or "cut" is chosen and the cell instantiates other cells, a dialog will been shown in which the mode can be selected:
When a cell is pasted into another layout and there is a "ghost cell" with that name, the pasted cell will replace the ghost cell. If there is a normal cell with that name, a new cell variant will be created and the name of the pasted cell will be changed by adding a suffix to create a unique name.
Copying a cell in deep copy mode from one layout to another provides a way to merge two layouts into one: simply copy the top cell of the first layout into the second one and instantiate both in a new top cell for example.