Back up your save if you choose to do this. I haven't run into any issues doing the below, but I also take 0 responsibility if your campaign bricks because of this.

For anyone that is interested in doing this I'm going to explain how I've done this here.

First, you'll need to duplicate the player board and survivor board from the game's assets. If you don't know how to do this go to Games > Workshop > Find this workshop item > Right click > Search > Drag the board onto your screen. Get the boards into position and then lock them. In my case I put the one new board I needed to the left of the 4 boards, below the milestones helper. I'm not sure where you'd place a 6th to have it neatly set up.

Second, you'll want to download this: https://steamcommunity.com/sharedfiles/filedetails/?id=2367244499&searchtext=counter and place a counter on each of the stats. You'll need to scale the counters up and down to make them fit respectively.

Third, you'll want to place 1 counter on each of the stats. If you want to move the counter you need to position your cursor to the edge of the counter itself and then you'll see the white border on it. Move it into place and then be sure to lock the counters down on top of the locked player board.

Now you're ready to go. That's it, really.

This is what mine looks like for reference: https://i.imgur.com/98zsN5i.png.

Obviously none of the scripting will work for these players you're adding. You'll have to calculate all the stats yourselves for movement, accuracy, strength, etc. This also means the Battle UI will not work for these players. When you pick up your newly added player minis it won't show movement range. None of the QoL things will work for these players.

In order to keep track of any stats for these newly added player boards and their character you'll have to modify their character sheet on the large Survivor sheet (https://i.imgur.com/Pgovvxs.png) that holds all survivors below the primary 4 player boards. Just have the 5th player use the sheet that is embedded in the Survivors section as if it were on their board.

A group of individuals that have some form of frontal lobe development should have no problem making this workaround function as needed. I've now run several showdowns using the above. Saved our campaign and reloaded it several dozen times. And have run into 0 problems, so far. That does not mean there will be no problems ever.

So back up your save if you choose to do this.

There's a *relatively* simple way to get the scripting working. If you do, you also don't need to add your own counters.

Similar disclaimer about 'this hasn't broken anything for me, but i'm not the mod owner' goes here.

Do the same as the above comment to duplicate the player boards
Likewise duplicate a player marker token from the same folder
No need to lock any of these pieces. Do yourself a favour and go and name these now.
To name something in TTS, right click on it, and the second row from the bottom is an interactable text box.
Name your player boards: "Player 5 Board" (Without the quotes), and "Player 6 Board"
Name your player markers: "Player 5 Marker" (still no quotes) and "Player 6 Marker"
This will help reduce errors later.

SAVE your module. Save it now. Save it. Do it. Then reopen your save. Make sure the changes you made are still there. If not, do it again. If they are, next step.

We'll be doing some script editing, but it is all simple to do.

Go modding > scripting. when you open this, it should be on the lua tab, and you should see a huge wall of code. Select all with ctrl A and paste it into an editor. Notepad++ is a good free editor, its what ill be describing, but it can also be done in notepad, its just a lot more work, and i'm going to be giving the directions in line references. Just download it.

We only need to add and change a few lines:
Find line 8296. It's the line that says: ["276ea7"] = { name = "Player 4 Board", noninteractible = true },
Copy and paste it so you have two duplicates of it below. On each of these two duplicates, change player 4 to 5 and 6 respectively.
Next you'll need to find the item GUIDs of the objects you created in TTS. Go back to TTS, right click on one of the player boards, and go to scripting. The bottom option in the text window will show its GUID. It is a 6 digit string that is unique to each object in TTS. When you created your new objects each one was assigned. So you need to match the GUIDs with player board 5 and 6 respectively. Mine looks like this, but your GUIDs will be different:
["276ea7"] = { name = "Player 4 Board", noninteractible = true },
["5126fe"] = { name = "Player 5 Board", noninteractible = true },
["32e136"] = { name = "Player 6 Board", noninteractible = true },

We're going to do the same thing with player markers. The code for these is directly below what you just edited. So now on line 8303, we're going to add two lines below it. You'll end up something like this, but again, your GUIDs will be different:
["9a6e00"] = { name = "Player 4 Marker" },
["27334a"] = { name = "Player 5 Marker" },
["c6d863"] = { name = "Player 6 Marker" },

Now we're going to be editing a few values
All we're changing is some 4s to some 6s.
Change the 4 on the following lines to a 6:
Line 7447
Line 9679
Line 10585
Line 14448
Line 14826
Line 14932

And that's it!

Save your code. Then go back to TTS. Back under modding > scripting, delete everything that is there, and replace it with the code you just edited. Then save and play.

Most of the scripting should work now.

If you want COMPLETE functionality, you just need to add a couple players to TTS.

1) The third button down the bar on the left of your screen is zones. Click that and go to hands. If you look at the bottom left of the table, there's 4 hands already there. Add two more in spaces that dont overlap. They dont need to be big. Once they are added, you can left-click them and assign a colour. I used purple and orange.

2) Go back to your player markers. You can right-click these and change color tint to match the new hands you just added. You'll notice that only the ring around the outside actually changes.

3) If you want the faces of the player markers to match, you just need to upload new art. I honestly just zoomed in on one of the other tokens, and took a screenshot. You can use any photo editor to shift the colour to whatever you want. Once you're happy with your edited piece, save it on your PC, and go back to TTS. Right click the player markers, and select the first option 'custom' for front and back images just find the colour-shifted images you saved to your PC. This should mean you can link figurines to these colours, and they'll match just like they do for players 1-4.

4) Finally, add the starting gear tiles to your new boards and save again.

If you followed instructions, all the scripting and all your buttons should work now. Congrats and enjoy.