espocrm/application/Espo/Modules/Crm/Resources/metadata/logicDefs/Case.json

{
    "fields": {
        "number": {
            "visible": {
                "conditionGroup": [
                    {
                        "type": "isNotEmpty",
                        "attribute": "id"
                    }
                ]
            }
        }
    }
}