Add this after line 809:

["assets/prefabs/deployable/tool cupboard/retro/cupboard.tool.retro.deployed.prefab"] = new ContainerConfiguration(),​

This is giving me an error on 810, position 14. I'm new to modifying cs files, did you mean to make a new line to past this, or add it onto the end itself of 809? I was making a fresh 810, positioning it in line with 809 spacing, and placing the string you gave

Here's what the whole block around it looks like for me:

            [JsonProperty("Containers by short prefab name")]
            private Dictionary<string, ContainerConfiguration> ContainersByShortPrefabName = new Dictionary<string, ContainerConfiguration>
            {
                ["assets/content/vehicles/boats/rhib/subents/rhib_storage.prefab"] = new ContainerConfiguration(),
                ["assets/content/vehicles/boats/rowboat/subents/rowboat_storage.prefab"] = new ContainerConfiguration(),
                ["assets/content/vehicles/modularcar/subents/modular_car_1mod_storage.prefab"] = new ContainerConfiguration(),
                ["assets/content/vehicles/modularcar/subents/modular_car_camper_storage.prefab"] = new ContainerConfiguration(),
                ["assets/content/vehicles/snowmobiles/subents/snowmobileitemstorage.prefab"] = new ContainerConfiguration(),
                ["assets/content/vehicles/submarine/subents/submarineitemstorage.prefab"] = new ContainerConfiguration(),
                ["assets/prefabs/deployable/composter/composter.prefab"] = new ContainerConfiguration(),
                ["assets/prefabs/deployable/dropbox/dropbox.deployed.prefab"] = new ContainerConfiguration(),
                ["assets/prefabs/deployable/fridge/fridge.deployed.prefab"] = new ContainerConfiguration(),
                ["assets/prefabs/deployable/hitch & trough/hitchtrough.deployed.prefab"] = new ContainerConfiguration(),
                ["assets/prefabs/deployable/hot air balloon/subents/hab_storage.prefab"] = new ContainerConfiguration(),
                ["assets/prefabs/deployable/large wood storage/box.wooden.large.prefab"] = new ContainerConfiguration(),
                ["assets/prefabs/deployable/small stash/small_stash_deployed.prefab"] = new ContainerConfiguration(),
                ["assets/prefabs/deployable/tool cupboard/cupboard.tool.deployed.prefab"] = new ContainerConfiguration(),
                ["assets/prefabs/deployable/tool cupboard/retro/cupboard.tool.retro.deployed.prefab"] = new ContainerConfiguration(),
                ["assets/prefabs/deployable/vendingmachine/vendingmachine.deployed.prefab"] = new ContainerConfiguration(),
                ["assets/prefabs/deployable/woodenbox/woodbox_deployed.prefab"] = new ContainerConfiguration(),
                ["assets/prefabs/misc/halloween/coffin/coffinstorage.prefab"] = new ContainerConfiguration(),
                ["assets/prefabs/misc/decor_dlc/storagebarrel/storage_barrel_b.prefab"] = new ContainerConfiguration(),
                ["assets/prefabs/misc/decor_dlc/storagebarrel/storage_barrel_c.prefab"] = new ContainerConfiguration(),
                ["assets/rust.ai/nextai/testridablehorse.prefab"] = new ContainerConfiguration(),
            };​

Cheers, that did it. It was sending me to the wrong place entirely when I looked for line 809. Appreciate you

That's weird. Are you not running v2.2.0? The lines I posted are 793-817 in my file.

you can just added it to the config without editing the plugin code 

 "assets/prefabs/deployable/tool cupboard/retro/cupboard.tool.retro.deployed.prefab": {
      "Enabled": true,
      "OffsetX": 476.5
    },