In the editor place a Zeus "Game Master" module and an accompanying player unit.
Name the player unit and enter that name into the "owner" field of the game maser module.
Place a "Set Editing Costs" module and under the "Delete" field enter a very high, negative value (I used "-1e10" as suggested in the "SHOW INFO" section for the "Set Editing Costs" module).
Synchronize the "Set Editing Costs" module to the "Game Master" module.
Preview the mission.
In the Zeus interface, place any object.
Select the object and press the "Delete" key.