Storybook: O painel de complementos não está sendo exibido - mas os botões ainda estão funcionando (?)

Descreva o bug
Estou usando o complemento de botões para meu projeto StencilJs e está funcionando tecnicamente (se eu definir o componente prob dentro da história, ele o está alterando, por exemplo: olhe para o arquivo de história e, em seguida, o componente, você verá que está configurado isso - e faz). mas não consigo ver o painel de complementos. Acho que fiz toda a configuração corretamente (addons.js, package.json, etc).

Eu tentei selecionar a opção show addons dentro do storybook em execução, mas nada é exibido.

Como estou administrando é com npm run storybook

Reproduzir
Passos para reproduzir o comportamento:

1. Lançar livro de histórias
2. Nenhum painel de complementos é visível na lateral ou inferior

Comportamento esperado
Espero ver o painel de complementos se eu tiver um complemento instalado para ser usado

Capturas de tela

Partes de codigo
Abaixo está meu .storybook / addons.js

import '@storybook/addon-a11y/register';
import '@storybook/addon-actions/register';
import '@storybook/addon-knobs/register';

Abaixo está o meu package.json

"scripts": {
    "build": "stencil build",
    "start": "stencil build --dev --watch --serve",
    "stencil.dev": "stencil build --dev --watch --docs",
    "storybook.dev": "./node_modules/.bin/start-storybook -p 8008 -c .storybook -s ./dist",
    "storybook": "npm run build && ./node_modules/.bin/concurrently  \"npm run stencil.dev\" \"npm run storybook.dev\"",
    "test": "stencil test --spec --e2e",
    "test.watch": "stencil test --spec --e2e --watch",
    "generate": "stencil generate"
  },
  "dependencies": {
    "@ionic/core": "^4.9.1"
  },
  "devDependencies": {
    "@stencil/core": "^1.7.0",
    "@stencil/less": "^1.0.0",
    "@stencil/utils": "0.0.5",
    "@stencil/webpack": "0.0.6",
    "@storybook/addon-a11y": "5.2.3",
    "@storybook/addon-actions": "5.2.3",
    "@storybook/addon-knobs": "5.2.3",
    "@storybook/addon-storysource": "5.2.3",
    "@storybook/addon-viewport": "5.2.3",
    "@storybook/addons": "5.2.3",
    "@storybook/cli": "5.2.3",
    "@storybook/html": "5.2.3",
    "@storybook/polymer": "5.2.3",
    "babel-core": "6.26.3",
    "babel-loader": "7.1.5",
    "babel-preset-env": "1.7.0",
    "lit-html": "1.1.1",
    "polymer-webpack-loader": "2.0.3",
    "ts-loader": "^5.4.5",
    "concurrently": "^4.1.0"
  }

Abaixo está meu .storybook / config.js

import { addDecorator, addParameters, configure } from '@storybook/polymer';
import { withA11y } from '@storybook/addon-a11y';
import { withKnobs } from '@storybook/addon-knobs';
import 'sumai-frontend';

addParameters({
  options: {
    /**
     * name to display in the top left corner
     * <strong i="6">@type</strong> {String}
     */
    name: 'Sumai Components',
    /**
     * URL for name in top left corner to link to
     * <strong i="7">@type</strong> {String}
     */
    url: '#',
    /**
     * show story component as full screen
     * <strong i="8">@type</strong> {Boolean}
     */
    isFullscreen: false,
    /**
     * display panel that shows a list of stories
     * <strong i="9">@type</strong> {Boolean}
     */
    showNav: true,
    /**
     * display panel that shows addon configurations
     * <strong i="10">@type</strong> {Boolean}
     */
    showPanel: true,
    /**
     * display floating search box to search through stories
     * <strong i="11">@type</strong> {Boolean}
     */
    showSearchBox: false,
    /**
     * show addon panel as a vertical panel on the right
     * <strong i="12">@type</strong> {string}
     */
    addonPanelInRight: true,
    /**
     * sorts stories
     * <strong i="13">@type</strong> {Boolean}
     */
    sortStoriesByKind: false,
    /**
     * regex for finding the hierarchy separator
     * <strong i="14">@example</strong>:
     *   null - turn off hierarchy
     *   /\// - split by `/`
     *   /\./ - split by `.`
     *   /\/|\./ - split by `/` or `.`
     * <strong i="15">@type</strong> {Regex}
     */
    hierarchySeparator: null,
    /**
     * regex for finding the hierarchy root separator
     * <strong i="16">@example</strong>:
     *   null - turn off multiple hierarchy roots
     *   /\|/ - split by `|`
     * <strong i="17">@type</strong> {Regex}
     */
    hierarchyRootSeparator: null,
    /**
     * sidebar tree animations
     * <strong i="18">@type</strong> {Boolean}
     */
    sidebarAnimations: true,
    /**
     * id to select an addon panel
     * <strong i="19">@type</strong> {String}
     */
    selectedAddonPanel: undefined, // The order of addons in the "Addon panel" is the same as you import them in 'addons.js'. The first panel will be opened by default as you run Storybook
    /**
     * enable/disable shortcuts
     * <strong i="20">@type</strong> {Boolean}
     */
    enableShortcuts: true // true by default
  }
});

const req = require.context('../src/components', true, /story.tsx$/);
function loadStories() {
  req.keys().forEach(filename => req(filename));
}
configure(loadStories, module);
addDecorator(withA11y);
addDecorator(withKnobs);

// HMR interface
if (module.hot) {
  // Capture hot update
  module.hot.accept('sumai-frontend', () => {
    document.location.reload();
  });
}

abaixo está minha história.tsx

import { storiesOf } from "@storybook/polymer";
import { text } from "@storybook/addon-knobs";

storiesOf("Basic Components", module)
  .add("Modal", () => {
    const el = document.createElement("sumai-full-width-image");
    el.name = text('Name', 'Namey');
    return el;
  });

Sistema:

System:
    OS: Linux 5.0 Ubuntu 19.04 (Disco Dingo)
    CPU: (4) x64 Intel(R) Core(TM) i7-8650U CPU @ 1.90GHz
  Binaries:
    Node: 10.15.3 - /usr/local/bin/node
    Yarn: 1.16.0 - /bin/yarn
    npm: 6.4.1 - /usr/local/bin/npm
  Browsers:
    Chrome: 75.0.3770.80
    Firefox: 69.0.2
  npmPackages:
    @storybook/addon-a11y: 5.2.3 => 5.2.3 
    @storybook/addon-actions: 5.2.3 => 5.2.3 
    @storybook/addon-knobs: 5.2.3 => 5.2.3 
    @storybook/addon-storysource: 5.2.3 => 5.2.3 
    @storybook/addon-viewport: 5.2.3 => 5.2.3 
    @storybook/addons: 5.2.3 => 5.2.3 
    @storybook/cli: 5.2.3 => 5.2.3 
    @storybook/html: 5.2.3 => 5.2.3 
    @storybook/polymer: 5.2.3 => 5.2.3

Contexto adicional