In description.ext:
MPsaveFile = 1; // 0: disabled - 1: enabled. Default: 0

Result: When enabled, instead of using the standard saving method the mission will use a shortened, MP compatible version where it only saves:

• Player's Location, Health, Inventory, Stats.
• Vehicles the players are currently driving (their damage, ammo, fuel etc).
• Editor placed and properly named vehicles also have their damage, ammo, fuel etc saved.
• Global Variables and setVariable values for named units/vehicles/objects.

Otherwise on reload the objects are loaded as if the mission was started fresh.

That way hosted missions would have a method of saving without generating potential issues and even crashes related to the current save system saving every single detail about the mission including damaged buildings, opened doors etc etc.

Benefits: Stability, file size, MP QoL.