ui/src/main/resources/jcr_root/libs/sling/commons/thumbnails/transformers/transparency/edit.json

 {
    "jcr:primaryType": "nt:unstructured",
    "sling:resourceType": "sling-cms/components/editor/slingform",
    "button": "Save",
    "fields": {
        "jcr:primaryType": "nt:unstructured",
        "sling:resourceType": "sling-cms/components/general/container",
        "alpha": {
            "jcr:primaryType": "nt:unstructured",
            "sling:resourceType": "sling-cms/components/editor/fields/text",
            "label": "Alpha",
            "required": true,
            "name": "alpha"
        }
    }
}