Do I understand that correctly: you want to copy and paste several units at one time?
Pull a rectangle over the units or click on each particular and add one with SHIFT!
You can also create "Groups" with Ctrl + Number like in the game, if You copy this lines into the user.con file in the startup folder:
map ("1", "editor", "uiSelectNumberGroup(1)")
map ("2", "editor", "uiSelectNumberGroup(2)")
map ("3", "editor", "uiSelectNumberGroup(3)")
map ("4", "editor", "uiSelectNumberGroup(4)")
map ("5", "editor", "uiSelectNumberGroup(5)")
map ("6", "editor", "uiSelectNumberGroup(6)")
map ("7", "editor", "uiSelectNumberGroup(7)")
map ("8", "editor", "uiSelectNumberGroup(8)")
map ("9", "editor", "uiSelectNumberGroup(9)")
map ("shift-1", "editor", "uiAddSelectNumberGroup(1)")
map ("shift-2", "editor", "uiAddSelectNumberGroup(2)")
map ("shift-3", "editor", "uiAddSelectNumberGroup(3)")
map ("shift-4", "editor", "uiAddSelectNumberGroup(4)")
map ("shift-5", "editor", "uiAddSelectNumberGroup(5)")
map ("shift-6", "editor", "uiAddSelectNumberGroup(6)")
map ("shift-7", "editor", "uiAddSelectNumberGroup(7)")
map ("shift-8", "editor", "uiAddSelectNumberGroup(8)")
map ("shift-9", "editor", "uiAddSelectNumberGroup(9)")
map ("control-1", "editor", "uiCreateNumberGroup(1)")
map ("control-2", "editor", "uiCreateNumberGroup(2)")
map ("control-3", "editor", "uiCreateNumberGroup(3)")
map ("control-4", "editor", "uiCreateNumberGroup(4)")
map ("control-5", "editor", "uiCreateNumberGroup(5)")
map ("control-6", "editor", "uiCreateNumberGroup(6)")
map ("control-7", "editor", "uiCreateNumberGroup(7)")
map ("control-8", "editor", "uiCreateNumberGroup(8)")
map ("control-9", "editor", "uiCreateNumberGroup(9)")
map ("control-0", "editor", "uiRemoveFromAnyNumberGroup")
map ("alt-1", "editor", "uiSelectNumberGroup(1) uiLookAtNumberGroup(1)")
map ("alt-2", "editor", "uiSelectNumberGroup(2) uiLookAtNumberGroup(2)")
map ("alt-3", "editor", "uiSelectNumberGroup(3) uiLookAtNumberGroup(3)")
map ("alt-4", "editor", "uiSelectNumberGroup(4) uiLookAtNumberGroup(4)")
map ("alt-5", "editor", "uiSelectNumberGroup(5) uiLookAtNumberGroup(5)")
map ("alt-6", "editor", "uiSelectNumberGroup(6) uiLookAtNumberGroup(6)")
map ("alt-7", "editor", "uiSelectNumberGroup(7) uiLookAtNumberGroup(7)")
map ("alt-8", "editor", "uiSelectNumberGroup(8) uiLookAtNumberGroup(8)")
map ("alt-9", "editor", "uiSelectNumberGroup(9) uiLookAtNumberGroup(9)")