Is this for panelizing or for creating copies of the layout?
The former isn’t supported in KiCAD (yet) and the latter is not a recommended way of doing things.
..
You can (crudely) create a panel from several pcb designs by starting PCBnew as a standalone application (Windows, C:\Program Files\KiCad\bin\pcbnew.exe) and then use the menu File>Append Board, but this will not keep links to any schematics either..
If this is your last step before generating gerbers, good, do it.
If not, don’t do it.
PS: the array function came from footprint pad array creation and has not been adopted/modified for layout use. Better do not use it in the layout editor unless you know what you’re doing. It is not doing what you think it does.
PPS: be careful..
PPPS: (on panelization)