-collapsible-content"><div class="qm-api-item-content"><div class="qm-api-description"><div class="qm-html-paragraph">A selector for the titlebar header element </div></div><div class="qm-api-default"><span class="qm-api-default-key">Default: </span><span class="qm-api-default-value">'.hx-titlebar-header'</span></div></div></div></div></div></div></div></div></div></div></div></div></div><div class="qm-api-group qm-api-event-group"><div class="qm-api-group-header qm-api-event-group-header qm-header-font">Ev