Please take a look at our documentation for button groups:

https://mdbootstrap.com/docs/angular/components/buttons-group/

Here is an example for vertical button group that is displayed in the center of the screen:

<div class="d-flex justify-content-center">
  <div class="btn-group-vertical" role="group" aria-label="Vertical button group">
    <button mdbBtn type="button" color="amber" class="waves-light" mdbWavesEffect>Button</button>
    <button mdbBtn type="button" color="amber" class="waves-light" mdbWavesEffect>Button</button>
    <button mdbBtn type="button" color="amber" class="waves-light" mdbWavesEffect>Button</button>
    <button mdbBtn type="button" color="amber" class="waves-light" mdbWavesEffect>Button</button>
    <button mdbBtn type="button" color="amber" class="waves-light" mdbWavesEffect>Button</button>
    <button mdbBtn type="button" color="amber" class="waves-light" mdbWavesEffect>Button</button>
  </div>
</div>

Edit, fix for buttons width:

.btn-group-vertical .btn {
    width: initial;
}