[Patrick]

I think it's not impossible, I've create this function in about 5 minutes, I am not sure if this is what you want, you could loop all the players who's inside the dm and they're connected, it would show the name tag.

pawn Код:

#if defined MAX_PLAYERS
    #undef MAX_PLAYERS
    #define MAX_PLAYERS 100 //if MAX_PLAYERS is more than 255, you should remove the 'char'
#endif

new
    bool: IsPlayerInDM [ MAX_PLAYERS char ]
;

main()
{
    new playerid = 0;
    ShowDMNameTag(playerid, true);
}

stock ShowDMNameTag(playerid, bool:on = true)
{
    new
        i = 0
    ;
    while(i < MAX_PLAYERS && IsPlayerConnected(i) && IsPlayerInDM[i] == true)
    {
        if(on == true)
        {
            ShowPlayerNameTagForPlayer(playerid, i, true);
        }
        else if(on == false)
        {
            ShowPlayerNameTagForPlayer(playerid, i, false);
        }
        i++;
    }
}