MAKE RESERVED SLOTS

To make reserved slots on your server, follow theses steps :

STEP 1 : Create description.ext inside your mission folder and past following code :

class CfgDebriefing
{

   class NOT_ALLOWED
   {
       title = "This is a reserved slot.";
       description = "This is a reserved slot. Please rejoin using a different slot. Reserved slots are clearly marked on each units description in the lobby as ( Reserved )";
       picture = "";
   };
};

STEP 2 : Create initServer.sqf inside your mission folder and past following code :

allowed = call compile preprocessFileLineNumbers "allowedIDs.txt";

STEP 3 : Create initPlayerServer.sqf inside your mission folder and past following code :

_player = _this select 0;
_uid = getPlayerUID _player;

if ( _player getVariable [ "reserved", false ] && { !( _uid in allowed ) } ) then {
[ [], "fnc_reservedSlot", _player ] call BIS_fnc_MP;
};

STEP 4 : Create initPlayerLocal.sqf inside your mission folder and past following code :

fnc_reservedSlot = {
   player enableSimulationGlobal false;
   ( "reserved" call BIS_fnc_rscLayer ) cutText [ "This is a reserved slot. Reserved slots are clearly marked in the lobby as ( Reserved ) . Please rejoin using a different slot.", "BLACK OUT", 1, true ];
   sleep 10;
   endMission "NOT_ALLOWED";
};

STEP 5 : Create allowedIDs.txt and place this file in the folder where your servers Arma3.exe is (if you rent server by Nitrado for exemple, use fileZilla to transfert text file to the server folder where arma.exe is), it keeps the IDs private as they are not transmitted with the mission and can be updated for all your missions in one place.

In this text file, past following code :

//Fill the ARRAY with allowed UIDs - steam IDs
//Look something like "76566179256348507"
[ ];

STEP 6 : choose units you want make "reserved" and past in the INIT box following code :

this setVariable ["Reserved", true]

Note : you can, in your unit parameters, change description to have something like "group leader (reserved)"

Save your map, dont forget to place allowedIDs.txt in the folder where is arma.exe (STEP 5 - in server side), export your map to multiplayer