chrome/browser/resources/web_app_internals/web_app_internals.html

<style>
  h2 {
    margin-bottom: 10px;
    margin-top: 0;
  }

  .section {
    margin: 10px;
    margin-bottom: 20px;
    padding: 5px;
  }

  .web-app {
    background-color: var(--highlight, #00000007);
    border-inline-start-color: rgb(0, 50, 220);
    border-inline-start-style: solid;
  }

  .highlight {
    --highlight: #eff;
  }

  .web-app-name {
    font-weight: bold;
  }
</style>

<h1>Web App Internals</h1>

<div class="section">
  BMO enabled: <b>[[isBmoEnabled_]]</b>
  <template is="dom-if" if="[[!isBmoEnabled_]]">
    <p>
      Web apps are using the extension system via bookmark apps, see
      <a href="chrome://extensions-internals">
       chrome://extensions-internals
      </a>
      for bookmark app details.
    </p>
    <p>
      Enable BMO via
      <a href="chrome://flags/#enable-desktop-pwas-without-extensions">
        chrome://flags/#enable-desktop-pwas-without-extensions.
      </a>
    </p>
  </template>
</div>

<div class="section">
  <h2>Page index:</h2>
  <template is="dom-repeat" items="[[webAppList_]]">
    <div>
      <a href="#[[item.id]]">
        <img src="chrome://app-icon/[[item.id]]/32">
        [[item.name]]
      </a>
    </div>
  </template>
  <a href="#external">Externally installed web app prefs</a>
</div>

<div class="section">
  <h2 id="details">Web apps details:</h2>
  <template is="dom-repeat" items="[[webAppList_]]">
    <div class="section web-app" id="[[item.id]]">
      <h2>[[item.name]]</h2>
      <img src="chrome://app-icon/[[item.id]]/128">
      <pre>[[item.debugInfo]]</pre>
    </div>
  </template>
</div>

<div class="section" id="external">
  <h2>Externally installed web app prefs:</h2>
  <pre>[[externallyInstalledWebAppPrefs_]]</pre>
</div>