x-side-collapsible-heading-closed">hx-side-collapsible-heading-closed</span><span class="qm-api-header-tags"></span></div></div></div></div><div class="qm-api-collapsible-content"><div class="qm-api-item-content"><div class="qm-api-description"><div class="qm-html-paragraph">The class to add to the heading to show when the collapsible is closed. This is rotated through 90 degrees. </div></div><div class="qm-api-group qm-api-extraClass-group"><div class="qm-api-group-header qm-api-extraClass-group-header qm-