[Mobhack]

You cannot split crews in deployment other than if they board a transport plane. The J key was provided for the deployment menu only in order to rejoin any such split units if the user subsequently offloaded them from the transport plane and wanted to deploy them elsewhere on map than where the plane was when he unloaded them.

There is no way to split crews in the deployment menu (battle or editor) other than that. But a scenario designer could buy a transport plane temporarily and load guns and then offload them as required where they should be, move the crew elsewhere, then delete the transport plane.

Once in the actual game, you can voluntarily split units with the @ key, if not retreating or routed. You have to move the correct crew back to its gun or AFV and leave them there at your end turn at pinned or better status in order to re crew the gun or vehicle. (No "J key" in game).

Therefore Once the new release is out, if you have the full game you can use the save as scenario function e.g. to goto turn 1 then split units, save off as a scenario then edit the scenario and move the crews. The abandoned units will be immobile so ensure they are in the right spot.