[解決済み] Angularマテリアルのmat-expansion-panelのコンテンツを中央に配置する。

.centered-content{
  align-content: center
  align-content: center
}

<mat-accordion>
  <!-- #docregion basic-panel -->
  <!-- #docregion hide-toggle -->
  <mat-expansion-panel hideToggle>
    <!-- #enddocregion hide-toggle -->
    <mat-expansion-panel-header>
      <mat-panel-title>
        This is the expansion title
      </mat-panel-title>
      <mat-panel-description>
        This is a summary of the content
      </mat-panel-description>
    </mat-expansion-panel-header>
    <div class="centered-content">
      <p>This is the primary content of the panel.</p>
    </div>
  </mat-expansion-panel>
  <!-- #enddocregion basic-panel -->


</mat-accordion>