gnome-control-center/panels/keyboard/cc-input-list-box.ui

<?xml version="1.0" encoding="UTF-8"?>
<interface>
  <template class="CcInputListBox" parent="AdwBin">
    <child>
      <object class="GtkListBox" id="listbox">
        <property name="selection-mode">none</property>
        <signal name="row_activated" handler="input_row_activated_cb" object="CcInputListBox" swapped="yes"/>
        <signal name="keynav_failed" handler="keynav_failed_cb" object="CcInputListBox" swapped="yes"/>
        <style>
          <class name="boxed-list"/>
        </style>
        <child>
          <object class="AdwButtonRow" id="add_input_row">
            <property name="title" translatable="yes">_Add Input Source</property>
            <property name="start-icon-name">list-add-symbolic</property>
            <property name="use-underline">True</property>
          </object>
        </child>
      </object>
    </child>
  </template>
</interface>