Absolutely agreed.

WeaponDisassembled EH should passed the disassembled weapon as 4th paramter.
This missing creates a potentiel bug in my project.

Would be great to cancel the weapon disassembly by returning false.
Or in a smarter way : to disable the disassembly feature by : weapon setVariable ["BIS_disable_weapon_disassembly", true]

The command cursorTarget can be used to get the disassembled weapon.
It works only for the local player. And this not a safe way to retrieve it.

To work also for units different from player, commands like nearestObject could also be used. But this is a very unsafe way.

BIS, please add this 4th parameter.

I tested the idea with the nearestObject command but it returned objNull. I bet the cursorTarget command will return the same (haven't tested). From this I deduce that the event handler triggers after the weapon is disassembled (after the weapon object is removed and replaced with backpacks).

I deduce that the event handler triggers after the weapon is disassembled

No, I thought too before testing it. But I succeed to retrieve the dismounted weapon with cursorTarget.
Maybe the near* commands don't work (too slow ?).

A simple script command like "disableWeaponDisassembly" would be the most appropriate. Global effect, of course.

The cursorTarget command can be used only if players disassemble the static weapon (missions with AI disabled). In a mission with AIs I can cheat by ordering an AI to disassemble the weapon since cursorTarget applies to player unit and will return objNull.

@d3nn16 - could you share the code for your cursorTarget workaround? :)

if (not isDedicated) then
{
waitUntil {not isNil "ZCM_PLAYER_IS_DEFINED"};

...

// track backpacks when disassembling static weapons
player addEventHandler
[

		"WeaponDisassembled",
		{
			(_this select 1) setVariable ["zgp_vehicle_group", cursorTarget getVariable ["zgp_vehicle_group", grpNull], true];
		}

];
};

This will update the weapon backpack object by adding a variable to it that tells the group of the player who disassembled it.

WeaponDisassembled and cursorTarget in R3F Logistics :

player addEventHandler ["WeaponDisassembled",

			{
				private ["_objet"];
				
				_objet = cursorTarget;
				
				if (!isNull _objet && {!isNull (_objet getVariable ["R3F_LOG_est_deplace_par", objNull])}) then
				{
					_objet setVariable ["R3F_LOG_est_deplace_par", objNull, true];
				};
			}];

Upvoted - we need what have been suggested here. I just did more tests, the original object reference is NOT objNull after the weapon is disassembled eg. _my50="B_HMG_01_F" createVehicle pos; The getPos on _my50 after it has been disassembled is a position on altis in the sea, so a workaround to get the reference to the weapon that was disassembled could be to check the cords against the sea pos, it should be safe as a weapon cannot be assembled in the sea, maybe that is why the sea cords was used? Anyway you can still get info on ammo and magazines on _my50 after its been disassembled. So _isDisassembled = surfaceIsWater (position _my50); used together with the EventHandler you can find out what weapon was just disassembled. Other info that could be useful is that if you do player moveInGunner _my50 (when disassembled) will put the 50 cal back where is was dismantled although bugged.