Twinkle block override

window.addEventListener("load", function() {
    Twinkle.block.blockGroups = [
        {
            label: 'Group label'
            list: [
                { label: 'description of preset #1', value: 'preset_1' }
                { label: 'description of preset #2', value: 'preset_2' }
            ]
        },
        {
            //...another group...
        }
    ];
}, false);