How to make 2 different textures for an item, 1 for a gui icon and another for when it is handheld

So, I got this json for my item, and I can't seem to get it working, I've been sitting here finding out how for an hour now and I seem to not understand how it works, What I want is for my item to have 2 separate textures, both 2D, 1 for the GUI icon, and another for when it is hand held, no it is not a 3D item but just another 2D texture, pls help

{
    "loader": "forge:separate_transforms",
    "parent": "item/handheld",
    "textures": {
      "layer0": "calamityremake:item/batbat"
  },
    "display": {
        "ground": {
            "rotation": [ 0, 0, 0 ],
            "translation": [ 0, 3, 0],
            "scale":[ 1, 1, 1 ]
        },
        "fixed": {
            "rotation": [ 0, 0, 0 ],
            "translation": [ 0, 0, 0],
            "scale":[ 1, 1, 1 ]
        },
        "thirdperson_righthand": {
            "rotation": [ 0, 90, 40 ],
            "translation": [ 0, 15, 2 ],
            "scale": [ 2.0, 2.0, 2.0 ]
        },
        "firstperson_righthand": {
            "rotation": [ 0, 90, 40 ],
            "translation": [ 0, 15, 2 ],
            "scale": [ 2.0, 2.0, 2.0 ]
        },
        "firstperson_lefthand": {
            "rotation": [ 0, 90, 40 ],
            "translation": [ 0, 15, 2 ],
            "scale": [ 2.0, 2.0, 2.0 ]
        }
    },
    "perspectives": {
        "gui": {
            "parent": "item/generated",
            "textures": {
                "layer0": "calamityremake:item/batbathud"
                },
                "gui_light": "front"
            }
        }
}