I don't know anything about the Scripteditor, but adding extra weapons to gear selection is very easy.
I take it you have a description.ext file. Copy and paste the blurb below, change the weapons as you like. Get the names from the weapon and ammo list in the Ed Depot - Tutes - References. For user created addon weapons the names should be included in the addon readme.
class Weapons
{
class binocular
{
count = 1;
};
class M21
{
count = 1;
};
class Steyr
{
count = 1;
};
class G36a
{
count = 1;
};
class XMS
{
count = 1;
};
class M16
{
count = 1;
};
class M16GrenadeLauncher
{
count = 1;
};
class M60
{
count = 1;
};
class kozlice
{
count = 1;
};
class MM1
{
count = 1;
};
class Mortar
{
count = 1;
};
class LAWLauncher
{
count = 1;
};
class CarlGustavLauncher
{
count = 1;
};
};
class Magazines
{
class M21
{
count = 9;
};
class SteyrMag
{
count = 9;
};
class G36aMag
{
count = 9;
};
class M4
{
count = 9;
};
class M16
{
count = 9;
};
class M16GrenadeLauncher
{
count = 9;
};
class M60
{
count = 9;
};
class kozliceball
{
count = 9;
};
class kozliceshell
{
count = 9;
};
class MM1magazine
{
count = 9;
};
class HandGrenade
{
count = 9;
};
class Mortar
{
count = 9;
};
class LAWLauncher
{
count = 3;
};
class CarlGustavLauncher
{
count = 1;
};
class Pipebomb
{
count = 3;
};
class Flare
{
count = 4;
};
class FlareRed
{
count = 4;
};
class FlareGreen
{
count = 4;
};
class FlareYellow
{
count = 4;
};
class SmokeShell
{
count = 4;
};
class SmokeShellRed
{
count = 4;
};
class SmokeShellGreen
{
count = 4;
};
};