Selecting properties on Call of Duty: Black Ops 3 will allow you to view all available DLC content, within this page you're given the option to remove segments of the game you deem unnecessary to your experience (Campaign, Multiplayer).
Deleting Campaign will remove the ability to play both Dead Ops Arcade 2 & Zombie Nightmares
Deleted content will be greyed out on the main menu.

Given the current state of CoD online security flaws throughout every PC port, it is not recommended that you play this title without one of the following fixes. Bullet points have been listed for both community fixes to help you choose the appropriate solution.

boiii client

Pros

• Allows cross progression between the base game & modded maps (XP, weapon kits).
  
• Allows the user to manually choose their rank/prestige/unlocks/Easter Egg progression.
  
• Unlocks all Black Market & Dr. Monty's Factory bonus content for free (unlimited mega uses).
  
• Emulates online servers allowing you to rank up without the need for an internet connection.

Cons

• Unable to host private lobby's without the use of a Virtual Private Network for LAN games (e.g. LogMeIn Hamachi) or setting up ones own dedicated server.
  
• Unable to unlock Steam Achievements.
  
• Inconsistent security updates for public play.
  
• More limited selection of compatible mods.
  
• Doesn't natively track playtime

Download boiii client here.[github.com]

T7patch by Serious

Pros

• Frequent security updates.
  
• can host private lobby's without the use of VPN.
  
• Ability to unlock Steam Achievements.
  
• Wider variety of mod support.

Subjective

• Ability to purchase/earn liquid divinium.

Cons

• Unable to cross progress between base game & modded maps (XP, weapon kits).
  
• All content has to be unlocked/earned/purchased legitimately.
  
• Relies on Steam servers which are more prone to maintenance/crashes.
  
• No offline progression.

Download T7patch by Serious here.[github.com]

I personally use both of these methods depending on state of play (e.g. if i'm playing solo or with friends/if i'm playing on Steam Deck).

Please note mods cannot be stacked but can be used on most custom maps.

Essential mods

Co-op Pause

Co-op pause is a simple script which allows you to pause online & split screen matches. It is advised not to move or shoot once the match has been paused to avoid potential crashes.

Download here.

Zombies Bots

For those of us who don't have friends to play with.

Download here.

Solo Easter Eggs

For those of us who don't have friends to play with.

Download here.

Unlock All

Unlocks all camos, attachment variants, and gobblegums. Does not work in public matches.

Download here.

Essential maps
Official maps faithfully recreated within Black Ops 3.

Call of the Dead
"A shipwrecked crew of fearless explorers are hopelessly stranded in an abandoned Siberian outpost. Their dream of discovering the true origins of the mysterious Element 115 unravels into a Hellish nightmare."

To note;

• Black Ops 1 arsenal.
  
• Base Gobblegum price is increased to 1500.
  
• Some Ultra-Rare Megas were banned due to performance issues.

Download here.

Nuketown Zombies
"Mass-energy equivalence, secret tests, crash-landing perks. Survive in the iconic Nuketown, where the past and the future come together."

To note;

• No gobblegum machines.
  
• not mod compatible.

Download here.

Die Rise
"Watch your step! Fight for survival atop the towers of doom, where dizzying heights and the relentless undead make a deadly combination."

To note;

• Black Ops 2 arsenal.
  
• No gobblegum machines.
  
• Patreon exclusive beta.

Download here.[www.patreon.com]

Mob of the Dead
"Battle the undead as you attempt to break free from the physical and metaphorical incarceration of Alcatraz Prison."

To note;

• Black Ops 2 arsenal.
  
• Patreon exclusive beta.

Download here.[www.patreon.com]

Mod load order
Selecting properties on Call of Duty: Black Ops 3 will allow you to view all subscribed workshop content, within this page you're given the option to organise your mod load list. This is a relatively new steam feature which can allow you to order your custom maps for the map selection menu to your liking. it is advised to have scripts & overhaul mods at the bottom of your load order to prevent unintended alterations to your map load order.

I mainly use this feature to order community remasters chronologically.

Mod info customisation
You can further customise your downloaded maps by navigating to
C:\Program files (x86)\Steam\steamapps\workshop\content\311210

From here, you can edit map descriptions and titles by opening their workshop.json as a text file, you can also replace map preview & loading images so long as their replacements are titled preview.png and loadingimage.png respectively.

I mainly use this feature to help custom maps appear more official and organised.

Skip boot up screen
You can delete the Black Ops 3 splash screen by navigating to
C:\Program files (86x)\Steam\steamapps\common\Call of Duty Black Ops III\video
The file is titled bo3_global_logo_sequence.mkv, deleting this file will increase the speed at which the game boots up. This will also delete the forest cutscene played after a zombies match while loading back into the lobby. It will be replaced by a missing texture checker board.

Fast restart map
You can fast restart a map as host by using the command /map_restart in the console, this can also be applied as a bind by navigating to
C:\Program files (86x)\Steam\steamapps\common\Call of Duty Black Ops III\players
The file is titled bindings_0.cfg and can be edited as a text document. Simply add "bind (?) /map_restart" to the bottom of the file on the 60th line then save. Be sure to edit the properties of this file and set to 'read only' to prevent it being wiped. This bind will only work on offline/modded servers.

Mod preload
You can force Black ops 3 to preload your custom maps with the launch command '+set fs_game usermaps'. This will skip the loading screen upon selecting a custom map on the main menu. This command is highly recommended for boiii users. This can also be used to pre load a specific overhaul mod by replacing 'usermaps' with the mods assigned number, this can be found within the 311210 folder.

Split screen fix
The black bars present while using split screen can be removed by changing your native resolution to a 4:3 equivalent, here are some examples;

1280x720 = 1024x768
1920x1080 = 1440x1080
2560X1440 = 1920x1440
3840x2160 = 2880x2160

Once changed, make sure your in game resolution is also set to your 4:3 equivalent. If your game is still showing black bars try swapping your game from full screen to windowed borderless or vice versa.

Boiii client username
You can change your username in game by using the command /name *insert name*

TBA: How to have steam track your playtime with boiii client via STL.