All mods for this game should be used with this mod application:
Tobey's BepInEx + MelonLoader Pack for Supermarket Simulator.
The reason this dual mod application exists is simple: some mods require BepInEx, while others require MLLoader. The creator combined both into one package. Don't confuse the two, the mod author should always tell you which one their mod uses.
A Quick Notice
I'm assuming you already know your way around Windows Explorer and zip extraction apps. If not, save yourself the frustration, this isn't a guide for basic Windows navigation.
Let's Begin
On your hard drive, navigate to the game folder.
It should be here:
Steam > steamapps > common > Supermarket Simulator
The folders I'm about to ask you to create are just safe places to download and store your mods. Nothing more, nothing less. You cannot activate or install mods to the game from these folders.
Right click on Supermarket Simulator, select New Folder, and name it Nexus Mods. This is where you'll put all your Nexus mods.
Right click on Nexus Mods, select New Folder, and name it Tobey's BepInEx. This is where you'll download and keep the master zip file for Tobey's BepInEx.
Right click on Nexus Mods again, select New Folder, and name it Stock Manager. This is where you'll download and keep the master zip file for Stock Manager.
That's how I prep and set up Nexus Mods for this or any other game. Now let's get it working.
Your folder structure should look like this
Concentrating only on the folders you just created:
Supermarket Simulator (Main Directory)
-> Nexus Mods (safe place to download and keep your mods)
--> Stock Manager (RDC Stock Manager zip should be here)
--> Tobey's BepInEx (Tobey's BepInEx + MelonLoader Pack zip should be here)
Using Tobey's BepInEx + MelonLoader Pack
Go to the folder you just made for Tobey's BepInEx.
Right click and drag the zipped file for Tobey's BepInEx into the Supermarket Simulator Main Directory. Let go of the right click, and when asked, select Copy.
Now right click on the Tobey's BepInEx + MelonLoaderPack zip file you just placed in the main directory. Hover over 7-Zip, then select Extract Here.
Do not unzip Tobey anywhere else except the main game directory. It will not work otherwise.
Once it's unzipped, you can safely delete the zipped file from the main directory, because you should have the master file stored in the Nexus Mods > Tobey's BepInEx folder you created earlier.
Launch the game as you normally would. This will set up Tobey and all its associated files and folders. You won't see anything happen in game, but I'd suggest staying on the main menu for about a minute, then quitting.
Go back to your hard drive where the game is installed. You should now see two new folders in the main directory called BepInEx and MLLoader.
Along with that, you should also see a folder called Plugins in the main directory. Click it, and you should see a file called Tobey.BepInExMelonLoadWizard.MLPlugin.dll.
That means Tobey was installed successfully. If you don't see it, you didn't follow the instructions correctly.
Now It's time to use your new mod: RDC Stock Manager
Before we do that, I'd suggest expanding the BepInEx and MLLoader folders. It will make the next steps easier.
BepInEx will have five folders inside. The one you'll need is plugins.
MLLoader will also have five folders inside. The one you'll need is Mods.
Using Windows Explorer, this is what the directories look like:
Supermarket Simulator (Main Directory)
-> BepInEx
--> cache
--> config
--> core
--> patchers
--> plugins (This is where mods for BepInEx go)
-> MLLoader
--> MelonLoader
--> Mods (This is where mods for MLLoader go)
--> Plugins
--> UserData
--> UserLibs
Getting mods to work
The mod we're working on today is called RDC Stock Manager.
Download it and put it in the Nexus Mods > Stock Manager folder we created earlier.
Now right click on the Stock Manager zip file, hover over 7-Zip, and select Extract Here.
This mod uses MLLoader, so drag the Stock Manager.dll file and copy it to the MLLoader > Mods folder. If done correctly, your order screen should show the mod working, it displays how much you have on the shelf and in the stockroom, color coded to catch your eye.
Other mods may use BepInEx. In that case, just drag the .dll file and copy it to the BepInEx > plugins folder.
My Mods
As with all mods, use them at your own risk, and make sure they are updated for the current version of the game.
I can't confirm whether mods disable achievements, because I never waste time chasing them. But there are people on the forum who say they don't affect achievements.
You must have these two applications for mods to work:
7-Zip
Tobey's BepInEx + MelonLoader Pack for Supermarket Simulator