D:\Games\steamapps\common\GarrysMod\garrysmod\addons\your-config\lua\horde\gamemode\custom\Halo.lua

Commands: I used: "horde_external_lua_config Halo" & "horde_external_lua_config Halo.lua"

Lua:

-- Example your-custom-config.lua
-- If you just want to configure items, leave enemies as empty. Vice versa.

CONFIG = {Halo}
CONFIG.name = "Halo" -- YOU MUST NAME IT! Used for horde_external_lua_config.
CONFIG.items = {

}

CONFIG.enemies = {
-- key and name must be the same!
-- Since key has to be unique, you can use npc name + wave for the key.
Elite = {
name = "Elite",
class = "npc_iv04_hr_elite_minor",
weight = 1, -- Relative weight to other enemies in the same wave.
wave = 1,
is_elite = false,
health_scale = 1,
damage_scale = 1,
reward_scale = 100,
model_scale = 1,
color = Color(0,255,0),
weapon = "",
},

Grunt = {
name = "Grunt",
class = "npc_iv04_hr_grunt_minor",
weight = 1, -- Relative weight to other enemies in the same wave.
wave = 1,
is_elite = false,
health_scale = 1,
damage_scale = 1,
reward_scale = 100,
model_scale = 1,
color = Color(255,0,0),
weapon = ""
},
Jackal = {
name = "Jackal",
class = "npc_iv04_hr_jackal_minor",
weight = 1, -- Relative weight to other enemies in the same wave.
wave = 1,
is_elite = false,
health_scale = 1,
damage_scale = 1,
reward_scale = 100,
model_scale = 1,
color = Color(255,0,0),
weapon = ""
},

Elite Major = {
name = "Elite Major",
class = "npc_iv04_hr_elite_major",
weight = 1, -- Relative weight to other enemies in the same wave.
wave = 2,
is_elite = false,
health_scale = 1,
damage_scale = 1,
reward_scale = 100,
model_scale = 1,
color = Color(0,255,0),
weapon = "",
},


Skirmisher = {
name = "Skirmisher",
class = "npc_iv04_hr_skirmisher_minor",
weight = 1, -- Relative weight to other enemies in the same wave.
wave = 2,
is_elite = false,
health_scale = 1,
damage_scale = 1,
reward_scale = 100,
model_scale = 1,
color = Color(0,255,0),
weapon = "",
},

Elite = {
name = "Elite Minor",
class = "npc_iv04_hr_elite_minor",
weight = 1, -- Relative weight to other enemies in the same wave.
wave = 2,
is_elite = false,
health_scale = 1,
damage_scale = 1,
reward_scale = 100,
model_scale = 1,
color = Color(0,255,0),
weapon = "",
},

Brute Minor = {
name = "Brute Minor",
class = "npc_iv04_hr_brute_minor",
weight = 1, -- Relative weight to other enemies in the same wave.
wave = 3,
is_elite = false,
health_scale = 1,
damage_scale = 1,
reward_scale = 100,
model_scale = 1,
color = Color(0,255,0),
weapon = "",
},

Brute Captain = {
name = "Brute Captain",
class = "npc_iv04_hr_brute_captain",
weight = 1, -- Relative weight to other enemies in the same wave.
wave = 3,
is_elite = false,
health_scale = 1,
damage_scale = 1,
reward_scale = 100,
model_scale = 1,
color = Color(0,255,0),
weapon = "",
},

Brute Chieftain = {
name = "Brute Captain",
class = "npc_iv04_hr_brute_chieftain",
weight = 1, -- Relative weight to other enemies in the same wave.
wave = 3,
is_elite = false,
health_scale = 1,
damage_scale = 1,
reward_scale = 100,
model_scale = 1,
color = Color(0,255,0),
weapon = "",
},

Elite Ultra = {
name = "Elite Ultra",
class = "npc_iv04_hr_elite_ultra",
weight = 1, -- Relative weight to other enemies in the same wave.
wave = 4,
is_elite = false,
health_scale = 1,
damage_scale = 1,
reward_scale = 100,
model_scale = 1,
color = Color(0,255,0),
weapon = "",
spawn_limit = 6,
},
Drone Minor = {
name = "Drone Minor",
class = "npc_iv04_hr_drone_minor",
weight = 1, -- Relative weight to other enemies in the same wave.
wave = 4,
is_elite = false,
health_scale = 1,
damage_scale = 1,
reward_scale = 100,
model_scale = 1,
color = Color(0,255,0),
weapon = "",
},

Elite General = {
name = "Elite General",
class = "npc_iv04_hr_elite_general",
weight = 1, -- Relative weight to other enemies in the same wave.
wave = 4,
is_elite = false,
health_scale = 1,
damage_scale = 1,
reward_scale = 100,
model_scale = 1,
color = Color(0,255,0),
weapon = "",
spawn_limit = 4,
},

Grunt Heavy = {
name = "Grunt Heavy",
class = "npc_iv04_hr_grunt_heavy",
weight = 1, -- Relative weight to other enemies in the same wave.
wave = 4,
is_elite = false,
health_scale = 1,
damage_scale = 1,
reward_scale = 100,
model_scale = 1,
color = Color(0,255,0),
weapon = "",
spawn_limit = 5,
},

Champion = {
name = "Champion",
class = "npc_iv04_hr_skirmisher_champion",
weight = 1, -- Relative weight to other enemies in the same wave.
wave = 5,
is_elite = false,
health_scale = 1,
damage_scale = 1,
reward_scale = 100,
model_scale = 1,
color = Color(0,255,0),
weapon = "",

},

Skirm = {
name = "Skirm",
class = "npc_iv04_hr_skirmisher_minor",
weight = 1, -- Relative weight to other enemies in the same wave.
wave = 5,
is_elite = false,
health_scale = 1,
damage_scale = 1,
reward_scale = 100,
model_scale = 1,
color = Color(0,255,0),
weapon = "",

},

Chieftain = {
name = "Chieftain",
class = "npc_iv04_hr_brute_chieftain",
weight = 1, -- Relative weight to other enemies in the same wave.
wave = 5,
is_elite = false,
health_scale = 1,
damage_scale = 1,
reward_scale = 100,
model_scale = 1,
color = Color(0,255,0),
weapon = "",
spawn_limit = 3,
},

Elite Major = {
name = "Elite Major",
class = "npc_iv04_hr_elite_major",
weight = 1, -- Relative weight to other enemies in the same wave.
wave = 6,
is_elite = false,
health_scale = 1,
damage_scale = 1,
reward_scale = 100,
model_scale = 1,
color = Color(0,255,0),
weapon = "",

},

Elite Ultra = {
name = "Elite Ultra",
class = "npc_iv04_hr_elite_ultra",
weight = 1, -- Relative weight to other enemies in the same wave.
wave = 6,
is_elite = false,
health_scale = 1,
damage_scale = 1,
reward_scale = 100,
model_scale = 1,
color = Color(0,255,0),
weapon = "",

},

Elite Zealot = {
name = "Elite Zealot",
class = "npc_iv04_hr_elite_zealot",
weight = 1, -- Relative weight to other enemies in the same wave.
wave = 6,
is_elite = false,
health_scale = 1,
damage_scale = 1,
reward_scale = 100,
model_scale = 1,
color = Color(0,255,0),
weapon = "",
spawn_limit = 8,

},

drop pod = {
name = "drop pod",
class = "npc_iv04_hr_droppod",
weight = 1, -- Relative weight to other enemies in the same wave.
wave = 7,
is_elite = false,
health_scale = 1,
damage_scale = 1,
reward_scale = 100,
model_scale = 1,
color = Color(0,255,0),
weapon = "",
spawn_limit = 8,

},
Elite = {
name = "Elite",
class = "npc_iv04_hr_elite_minor",
weight = 1, -- Relative weight to other enemies in the same wave.
wave = 7,
is_elite = false,
health_scale = 1,
damage_scale = 1,
reward_scale = 100,
model_scale = 1,
color = Color(0,255,0),
weapon = "",


},

Elite Zealot = {
name = "Elite Zealot",
class = "npc_iv04_hr_elite_zealot",
weight = 1, -- Relative weight to other enemies in the same wave.
wave = 8,
is_elite = false,
health_scale = 1,
damage_scale = 1,
reward_scale = 1000,
model_scale = 1,
color = Color(0,255,0),
weapon = "",


},

Chieftain = {
name = "Chieftain",
class = "npc_iv04_hr_brute_chieftain",
weight = 1, -- Relative weight to other enemies in the same wave.
wave = 8,
is_elite = false,
health_scale = 1,
damage_scale = 1,
reward_scale = 1000,
model_scale = 1,
color = Color(0,255,0),
weapon = "",


},

Murmillo = {
name = "Murmillo",
class = "npc_iv04_hr_skirmisher_murmillo",
weight = 1, -- Relative weight to other enemies in the same wave.
wave = 8,
is_elite = false,
health_scale = 1,
damage_scale = 1,
reward_scale = 100,
model_scale = 1,
color = Color(0,255,0),
weapon = "",


},

Elite Zealot = {
name = "Zealot",
class = "npc_iv04_hr_elite_zealot",
weight = 1, -- Relative weight to other enemies in the same wave.
wave = 9,
is_elite = false,
health_scale = 1,
damage_scale = 1,
reward_scale = 1000,
model_scale = 1,
color = Color(0,255,0),
weapon = "",


},

Field Marshall = {
name = "Field Marshall",
class = "npc_iv04_hr_elite_field_marshall",
weight = 1, -- Relative weight to other enemies in the same wave.
wave = 9,
is_elite = false,
health_scale = 1,
damage_scale = 1,
reward_scale = 1000,
model_scale = 1,
color = Color(0,255,0),
weapon = "",


},

Scarab = {
name = "Scarab",
class = "npc_iv04_hr_scarab",
weight = 1, -- Relative weight to other enemies in the same wave.
wave = 10,
is_elite = true,
health_scale = 1,
damage_scale = 1,
reward_scale = 100,
model_scale = 2,
color = Color(255,0,0),
weapon = "",
spawn_limit = 1
boss_properties = {is_boss=true, end_wave=true, unlimited_enemies_spawn=false, enemies_spawn_threshold=0.5, music_duration=105}, -- optional, boss settings

},

Field Marshall = {
name = "Field Marshall",
class = "npc_iv04_hr_elite_field_marshall",
weight = 1, -- Relative weight to other enemies in the same wave.
wave = 10,
is_elite = false,
health_scale = 1,
damage_scale = 1,
reward_scale = 1000,
model_scale = 1,
color = Color(0,255,0),
weapon = "",
spawn_limit = 20


},
}

--------------------------------------------------------------------------------------------------------------------

Below is working version of the lua if anyone wants to use it.

--------------------------------------------------------------------------------------------------------------------
-- Example your-custom-config.lua
-- If you just want to configure items, leave enemies as empty. Vice versa.

CONFIG = {}
CONFIG.name = "Halo3" -- YOU MUST NAME IT! Used for horde_external_lua_config.
CONFIG.items = {}

CONFIG.enemies = {
-- key and name must be the same!
-- Since key has to be unique, you can use npc name + wave for the key.
Elite1 = {
name = "Elite1",
class = "npc_iv04_hr_elite_minor",
weight = 1, -- Relative weight to other enemies in the same wave.
wave = 1,
is_elite = false,
health_scale = 1,
damage_scale = 1,
reward_scale = 100,
model_scale = 1,

weapon = "",
},
Grunt1 = {
name = "Grunt1",
class = "npc_iv04_hr_grunt_minor",
weight = 1, -- Relative weight to other enemies in the same wave.
wave = 1,
is_elite = false,
health_scale = 1,
damage_scale = 1,
reward_scale = 100,
model_scale = 1,

weapon = "",
},
Jackal1 = {
name = "Jackal1",
class = "npc_iv04_hr_jackal_minor",
weight = 1, -- Relative weight to other enemies in the same wave.
wave = 1,
is_elite = false,
health_scale = 1,
damage_scale = 1,
reward_scale = 100,
model_scale = 1,

weapon = "",
},
Elite_Major = {
name = "Elite_Major",
class = "npc_iv04_hr_elite_major",
weight = 1, -- Relative weight to other enemies in the same wave.
wave = 2,
is_elite = false,
health_scale = 1,
damage_scale = 1,
reward_scale = 100,
model_scale = 1,

weapon = "",
},
Skirmisher = {
name = "Skirmisher",
class = "npc_iv04_hr_skirmisher_minor",
weight = 1, -- Relative weight to other enemies in the same wave.
wave = 2,
is_elite = false,
health_scale = 1,
damage_scale = 1,
reward_scale = 100,
model_scale = 1,

weapon = "",
},
Elite_Minor = {
name = "Elite_Minor",
class = "npc_iv04_hr_elite_minor",
weight = 1, -- Relative weight to other enemies in the same wave.
wave = 2,
is_elite = false,
health_scale = 1,
damage_scale = 1,
reward_scale = 100,
model_scale = 1,

weapon = "",
},
Brute_Minor1 = {
name = "Brute_Minor1",
class = "npc_iv04_hr_brute_minor",
weight = 1, -- Relative weight to other enemies in the same wave.
wave = 3,
is_elite = false,
health_scale = 1,
damage_scale = 1,
reward_scale = 100,
model_scale = 1,

weapon = "",
},
Brute_Captain1 = {
name = "Brute_Captain1",
class = "npc_iv04_hr_brute_captain",
weight = 1, -- Relative weight to other enemies in the same wave.
wave = 3,
is_elite = false,
health_scale = 1,
damage_scale = 1,
reward_scale = 100,
model_scale = 1,

weapon = "",
},
Brute_Captainn1 = {
name = "Brute_Captainn1",
class = "npc_iv04_hr_brute_chieftain",
weight = 1, -- Relative weight to other enemies in the same wave.
wave = 3,
is_elite = false,
health_scale = 1,
damage_scale = 1,
reward_scale = 100,
model_scale = 1,

weapon = "",
},
Elite_Ultra1 = {
name = "Elite_Ultra1",
class = "npc_iv04_hr_elite_ultra",
weight = 1, -- Relative weight to other enemies in the same wave.
wave = 4,
is_elite = false,
health_scale = 1,
damage_scale = 1,
reward_scale = 100,
model_scale = 1,

weapon = "",

},

GM1 = {
name = "GM1",
class = "npc_iv04_hr_grunt_minor",
weight = 2.4, -- Relative weight to other enemies in the same wave.
wave = 4,
is_elite = false,
health_scale = 1,
damage_scale = 1,
reward_scale = 100,
model_scale = 1,

weapon = "",

},

Elite_General1 = {
name = "Elite_General1",
class = "npc_iv04_hr_elite_general",
weight = .5, -- Relative weight to other enemies in the same wave.
wave = 4,
is_elite = false,
health_scale = 1,
damage_scale = 1,
reward_scale = 100,
model_scale = 1,

weapon = "",

},
Grunt_Heavy1 = {
name = "Grunt_Heavy1",
class = "npc_iv04_hr_grunt_heavy",
weight = 1, -- Relative weight to other enemies in the same wave.
wave = 4,
is_elite = false,
health_scale = 1,
damage_scale = 1,
reward_scale = 100,
model_scale = 1,

weapon = "",

},
Champion = {
name = "Champion",
class = "npc_iv04_hr_skirmisher_champion",
weight = 1, -- Relative weight to other enemies in the same wave.
wave = 5,
is_elite = false,
health_scale = 1,
damage_scale = 1,
reward_scale = 100,
model_scale = 1,

weapon = "",
},
Skirm = {
name = "Skirm",
class = "npc_iv04_hr_skirmisher_minor",
weight = 1, -- Relative weight to other enemies in the same wave.
wave = 5,
is_elite = false,
health_scale = 1,
damage_scale = 1,
reward_scale = 100,
model_scale = 1,

weapon = "",
},
Chieftain2 = {
name = "Chieftain",
class = "npc_iv04_hr_brute_chieftain",
weight = .2, -- Relative weight to other enemies in the same wave.
wave = 5,
is_elite = false,
health_scale = 1,
damage_scale = 1,
reward_scale = 100,
model_scale = 1,

weapon = "",

},
Elite_Major2 = {
name = "Elite_Major2",
class = "npc_iv04_hr_elite_major",
weight = 1, -- Relative weight to other enemies in the same wave.
wave = 6,
is_elite = false,
health_scale = 1,
damage_scale = 1,
reward_scale = 100,
model_scale = 1,

weapon = "",
},
Elite_Ultra2 = {
name = "Elite_Ultra2",
class = "npc_iv04_hr_elite_ultra",
weight = 1, -- Relative weight to other enemies in the same wave.
wave = 6,
is_elite = false,
health_scale = 1,
damage_scale = 1,
reward_scale = 100,
model_scale = 1,

weapon = "",
},
Elite_Zealot1 = {
name = "Elite_Zealot1",
class = "npc_iv04_hr_elite_zealot",
weight = .4, -- Relative weight to other enemies in the same wave.
wave = 6,
is_elite = false,
health_scale = 1,
damage_scale = 1,
reward_scale = 100,
model_scale = 1,

weapon = "",

},

Elite3 = {
name = "Elite3",
class = "npc_iv04_hr_elite_minor",
weight = 1, -- Relative weight to other enemies in the same wave.
wave = 7,
is_elite = false,
health_scale = 1,
damage_scale = 1,
reward_scale = 100,
model_scale = 1,

weapon = "",
},
Elite_Zealot2 = {
name = "Elite_Zealot2",
class = "npc_iv04_hr_elite_zealot",
weight = 1, -- Relative weight to other enemies in the same wave.
wave = 8,
is_elite = false,
health_scale = 1,
damage_scale = 1,
reward_scale = 1000,
model_scale = 1,

weapon = "",
},
Chieftain4 = {
name = "Chieftain4",
class = "npc_iv04_hr_brute_chieftain",
weight = 1, -- Relative weight to other enemies in the same wave.
wave = 8,
is_elite = false,
health_scale = 1,
damage_scale = 1,
reward_scale = 1000,
model_scale = 1,

weapon = "",
},
Murmillo = {
name = "Murmillo",
class = "npc_iv04_hr_skirmisher_murmillo",
weight = 1, -- Relative weight to other enemies in the same wave.
wave = 8,
is_elite = false,
health_scale = 1,
damage_scale = 1,
reward_scale = 100,
model_scale = 1,

weapon = "",
},
Zealot3 = {
name = "Zealot3",
class = "npc_iv04_hr_elite_zealot",
weight = 1, -- Relative weight to other enemies in the same wave.
wave = 9,
is_elite = false,
health_scale = 1,
damage_scale = 1,
reward_scale = 1000,
model_scale = 1,

weapon = "",
},
Field_Marshall5 = {
name = "Field_Marshall5",
class = "npc_iv04_hr_elite_field_marshall",
weight = 1, -- Relative weight to other enemies in the same wave.
wave = 9,
is_elite = false,
health_scale = 1,
damage_scale = 1,
reward_scale = 1000,
model_scale = 1,

weapon = "",
},
Field_Marshall6 = {
name = "Field_Marshall6",
class = "npc_iv04_hr_elite_field_marshall",
weight = 1, -- Relative weight to other enemies in the same wave.
wave = 10,
is_elite = false,
health_scale = 1,
damage_scale = 1,
reward_scale = 1000,
model_scale = 1,

weapon = "",
spawn_limit = 20
},
Scarab = {
name = "Scarab",
class = "npc_iv04_hr_scarab",
weight = 1, -- Relative weight to other enemies in the same wave.
wave = 10,
is_elite = true,
health_scale = 1,
damage_scale = 1,
reward_scale = 100,
model_scale = 1,
boss_properties = {is_boss=true, end_wave=true, unlimited_enemies_spawn=false, enemies_spawn_threshold=0.5}, -- optional, boss settings
weapon = "",
spawn_limit = 1
}
}