1. Open up the editor.
2. Place a flying heli, name it 'heli1'.
3. Place a paratrooper, make it the player.
4. Move the player as cargo of the heli.
5. Preview, eject and open your parachute.
6. Once you're flying in your parachute, open the debug window and type in: player action ["EJECT", heli1].
The player will eject the parachute.
EDIT: Simplified the steps to reproduce.