modal-stack.component.html

<h3>Modal nesting tests</h3>

<ng-template #t let-modal>
  <div class="modal-header">
    <h4 class="modal-title">Modal with nested popups</h4>
    <button type="button" class="close" aria-label="Close" (click)="modal.dismiss()">
      <span aria-hidden="true">&times;</span>
    </button>
  </div>
  <div class="modal-body">
    <!-- modal -->
    <button id="open-inner-modal" class="btn btn-lg btn-outline-primary" (click)="openSecondModal()">Open stack modal</button>
  </div>
</ng-template>

<button class="btn btn-outline-secondary ml-2" type="button" id="open-modal" (click)="openModal(t)">Open Modal</button>