How to use the babylonjs-editor.Window function in babylonjs-editor

private _addVariable (): void {
        // Create window
        const window = new Window('GraphToolAddVariable');
        window.buttons = ['Ok', 'Cancel'];
        window.width = 450;
        window.height = 170;
        window.body = `<div style="width: 100%; height: 100%;" id="GRAPH-TOOL-ADD-VARIABLE"></div>`;
        window.open();

        // Create form
        const form = new Form('GRAPH-TOOL-ADD-VARIABLE');
        form.fields = [
            { name: 'name', type: 'text', required: true, html: { span: 10, caption: 'The name of the variable.' } },
            { name: 'type', type: 'list', required: true, html: { span: 10, caption: 'Format' }, options: {
                items: ['String', 'Boolean', 'Number', 'Vector 2D', 'Vector 3D', 'Vector 4D'] 
            } }
        ];
        form.build('GRAPH-TOOL-ADD-VARIABLE');
        form.element.record['name'] = 'My Variable';

private async _editVariable (id: number): Promise {
        const v = this.object.graph.variables[id];

        // Create window
        const window = new Window('GraphToolAddVariable');
        window.buttons = ['Ok', 'Cancel'];
        window.width = 450;
        window.height = 170;
        window.body = `<div style="width: 100%; height: 100%;" id="GRAPH-TOOL-EDIT-VARIABLE"></div>`;
        window.open();

        // Create form
        const form = new Form('GRAPH-TOOL-EDIT-VARIABLE');
        form.fields = [
            { name: 'name', type: 'text', required: true, html: { span: 10, caption: 'The name of the variable.' } }
        ];
        switch (this._getType(v.value)) {
            case 'String':
                form.fields.push({ name: 'value', type: 'text', required: true, html: { span: 10, caption: 'Value' } });
                break;
            case 'Number':