NOTE: For you people too lazy to scroll around, if you have LWS' leader pack it will always read 0 squad cohesion level at squad select. That's what the additional squad cohesion level at the screen where you go to add a soldier is for. 

Otherwise it generally works with any other mod unless specified down below in the incompatibilities section. Yes that means larger squad size mods works with this. 

The values shown only update once you go to add a new soldier to the squad, not when you remove one. 

The system works as such with the default values: 

Below 300 points, squads work as normal 

At 300 to 600 points, a deployed squad gains a buff of +2 Aim, +2 Def, +1 Mobility, +5 Hacking, +5 Psi Offense, and +10 Will 

At 600 to 1200 points, a deployed squad gains a buff of +5 aim, +5 Def, +2 Crit Chance, +10 hacking, +7 Psi Offense, +1 Mobility and +15 Will 

And past 1200 points, a deployed squad will gain a buff of +5 aim, +5 Def, +5 crit chance, +2 Mobility, +15 hacking, +10 Psi Offense, and +20 Will 

These buffs and more can be adjusted at the XComSquadCohesion.ini located in (wherever XCOM 2 is installed)steamapps\workshop\content\268500\660665065\Config 


Squadmates earn cohesion between each other by: 


Vanilla Methods
Healing a soldier for +5 points 
Stabilizing a downed soldier for +15 points 
Carrying a downed soldier out of the battlefield for +30 points 
And killing an enemy flanking a soldier for +10 points 

These are all governed by XComGameData_XpData.ini that comes with the mod located in(wherever XCOM 2 is installed)steamapps\workshop\content\268500\660665065\Config. These also are all between the two soldiers that do them, no more. 

Mod-added Methods
At the end of every mission, a change in cohesion between all squadmates (IE each squadmate will get the bonus or penalty with every other squadmate) will be done by getting: 
Was the mission done? +5 points. 
Was the mission flawless in terms of soldier injuries and fatalities? +5 points more. 
How many ayys were killed? Get 10% of that in points. 
Did anybody die? -3 points per death. 
Did anybody get captured? -2 points per capture. 
Did anybody get injured? -1 points per injury 

Like the buffs above, these can be adjusted at the XComSquadCohesion.ini located in (wherever XCOM 2 is installed)steamapps\workshop\content\268500\660665065\Config 


Penalties
In addition to the above, a soldier dying in a squad with some cohesion will cause everybody who knew that soldier well enough to roll for shaken. 

By default: 

If they didn't know them that well, nothing happens. 

Each soldier in a low cohesion relationship with the dead soldier (25) will have a 20% chance of getting Shaken if a soldier ends up dying in the mission. 

Each soldier in a med cohesion relationship with the dead soldier (50) will have a 40% chance of getting Shaken if a soldier ends up dying in the mission. 

Each soldier in a high cohesion relationship with the dead soldier (75) will have a 70% chance of getting Shaken if a soldier ends up dying in the mission. 

You can get a rough overview of soldiers relations to one another via their cohesion ratings in the personnel lists, along with seeing exact scores in the Armory Menu. 

The vanilla chance of Shaken being applied to a soldier that got gravely wounded is left untouched. 


Cosmetic/Quality-Of-Life Features
Individual relationship scores should be viewable by clicking on the Relationships button when viewing a soldier in the Armory. 

There is now a squads organization feature at squad select, you can now save squad compositions you know work well with each other. 

Can't figure out what to name the squad you have? Just leave it blank, and the mod will auto-generate a squad name to go with the given squad composition. 


Incompatibilities?

This mod uses UIScreenListeners to do all the major work, however some mods still conflict like: 

LWS's Leader Pack (WORKAROUND IMPLEMENTED) - this mod does things to the squad select screen that can result in...funny things happening to other things UI-related that needs to put things on there (IE like the Fatigue mod's reported incompatibility with it), such as zeroing out the total cohesion level. A workaround cohesion level has been implemented. 

Thanks to asdf0716 for discovering the source of this. 

Toolbox Incompatibility 
LWS's Toolbox mod is incompatible with the Squad Management portion of the mod. Can't seem to find a way to resolve this. 

Mystery Conflict (Second Wave Reborn, maybe?) - an unidentified conflict with another mod may cause the game to crash if you try loading a tactical save. It might be partially due to Second Wave Reborn, though a couple people have reported crashes without it. 

Update: Some people are reporting it has stopped crashing now, need confirmation from multiple sources before I'll consider this resolved. 

Please go here to report any issues along that line. 

I'm using a 21:9 Screen and I can't find the Relationship button 

Change the following in the .ini from 
[SquadCohesion.RM_ArmoryMenu_ScreenListener] 
POSITION_X=-250 
POSITION_Y=70 

to 

[SquadCohesion.RM_ArmoryMenu_ScreenListener] 
POSITION_X=-850 
POSITION_Y=70 

Credits
Full credit to Falcon and his Uniforms Manager mod, which this mod uses a modified version of its code for the squad management functionality.